Include mailbox API version in local and remote mailbox properties

This changes the format of the mailbox properties update message, so
the major version of the client is bumped.

bramble-api/src/main/java/org/briarproject/bramble/api/client/ClientHelper.java

@@ -21,8 +21,6 @@ import java.security.GeneralSecurityException;
 import java.util.Collection;
 import java.util.Map;
 
-import javax.annotation.Nullable;
-
 @NotNullByDefault
 public interface ClientHelper {
 
@@ -127,15 +125,13 @@ public interface ClientHelper {
 			BdfDictionary properties) throws FormatException;
 
 	/**
-	 * Parse and validate the property dictionary of a Mailbox property update
+	 * Parse and validate the elements of a Mailbox property update message.
-	 * message.
 	 *
-	 * @return the properties for using the Mailbox, or null if there is no
+	 * @return the parsed update message
-	 * Mailbox available
+	 * @throws FormatException if the message elements are invalid
-	 * @throws FormatException if the properties are not valid
 	 */
-	@Nullable
 	MailboxPropertiesUpdate parseAndValidateMailboxPropertiesUpdate(
+			BdfList clientSupports, BdfList serverSupports,
 			BdfDictionary properties) throws FormatException;
 
 	/**

bramble-api/src/main/java/org/briarproject/bramble/api/mailbox/MailboxPropertiesUpdate.java

@@ -2,40 +2,27 @@ package org.briarproject.bramble.api.mailbox;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
+import java.util.List;
+
 import javax.annotation.concurrent.Immutable;
 
 @Immutable
 @NotNullByDefault
 public class MailboxPropertiesUpdate {
 
-	private final String onion;
+	boolean hasMailbox;
-	private final MailboxAuthToken authToken;
+	private final List<MailboxVersion> clientSupports;
-	private final MailboxFolderId inboxId;
-	private final MailboxFolderId outboxId;
 
-	public MailboxPropertiesUpdate(String onion,
+	public MailboxPropertiesUpdate(List<MailboxVersion> clientSupports) {
-			MailboxAuthToken authToken, MailboxFolderId inboxId,
+		this.hasMailbox = false;
-			MailboxFolderId outboxId) {
+		this.clientSupports = clientSupports;
-		this.onion = onion;
-		this.authToken = authToken;
-		this.inboxId = inboxId;
-		this.outboxId = outboxId;
 	}
 
-	public String getOnion() {
+	public List<MailboxVersion> getClientSupports() {
-		return onion;
+		return clientSupports;
 	}
 
-	public MailboxAuthToken getAuthToken() {
+	public boolean hasMailbox() {
-		return authToken;
+		return hasMailbox;
 	}
-
-	public MailboxFolderId getInboxId() {
-		return inboxId;
-	}
-
-	public MailboxFolderId getOutboxId() {
-		return outboxId;
-	}
-
 }

bramble-api/src/main/java/org/briarproject/bramble/api/mailbox/MailboxPropertiesUpdateMailbox.java

@@ -0,0 +1,51 @@
+package org.briarproject.bramble.api.mailbox;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import java.util.List;
+
+import javax.annotation.concurrent.Immutable;
+
+@Immutable
+@NotNullByDefault
+public class MailboxPropertiesUpdateMailbox extends MailboxPropertiesUpdate {
+	private final List<MailboxVersion> serverSupports;
+	private final String onion;
+	private final MailboxAuthToken authToken;
+	private final MailboxFolderId inboxId;
+	private final MailboxFolderId outboxId;
+
+	public MailboxPropertiesUpdateMailbox(List<MailboxVersion> clientSupports,
+			List<MailboxVersion> serverSupports, String onion,
+			MailboxAuthToken authToken, MailboxFolderId inboxId,
+			MailboxFolderId outboxId
+	) {
+		super(clientSupports);
+		this.hasMailbox = true;
+		this.serverSupports = serverSupports;
+		this.onion = onion;
+		this.authToken = authToken;
+		this.inboxId = inboxId;
+		this.outboxId = outboxId;
+	}
+
+	public String getOnion() {
+		return onion;
+	}
+
+	public MailboxAuthToken getAuthToken() {
+		return authToken;
+	}
+
+	public MailboxFolderId getInboxId() {
+		return inboxId;
+	}
+
+	public MailboxFolderId getOutboxId() {
+		return outboxId;
+	}
+
+	public List<MailboxVersion> getServerSupports() {
+		return serverSupports;
+	}
+}

bramble-api/src/main/java/org/briarproject/bramble/api/mailbox/MailboxPropertyManager.java

@@ -20,7 +20,7 @@ public interface MailboxPropertyManager {
 	/**
 	 * The current major version of the mailbox property client.
 	 */
-	int MAJOR_VERSION = 0;
+	int MAJOR_VERSION = 1;
 
 	/**
 	 * The current minor version of the mailbox property client.

bramble-api/src/main/java/org/briarproject/bramble/api/mailbox/MailboxSettingsManager.java

@@ -7,6 +7,8 @@ import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.lifecycle.LifecycleManager;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
+import java.util.List;
+
 import javax.annotation.Nullable;
 
 @NotNullByDefault
@@ -49,7 +51,8 @@ public interface MailboxSettingsManager {
 		 * @param txn A read-write transaction
 		 * @param ownOnion Our new mailbox's onion (56 base32 chars)
 		 */
-		void mailboxPaired(Transaction txn, String ownOnion)
+		void mailboxPaired(Transaction txn, String ownOnion,
+				List<MailboxVersion> serverSupports)
 				throws DbException;
 
 		/**

bramble-api/src/main/java/org/briarproject/bramble/api/mailbox/RemoteMailboxPropertiesUpdateEvent.java

@@ -4,7 +4,6 @@ import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
-import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
 
 /**
@@ -16,11 +15,10 @@ import javax.annotation.concurrent.Immutable;
 public class RemoteMailboxPropertiesUpdateEvent extends Event {
 
 	private final ContactId contactId;
-	@Nullable
 	private final MailboxPropertiesUpdate mailboxPropertiesUpdate;
 
 	public RemoteMailboxPropertiesUpdateEvent(ContactId contactId,
-			@Nullable MailboxPropertiesUpdate mailboxPropertiesUpdate) {
+			MailboxPropertiesUpdate mailboxPropertiesUpdate) {
 		this.contactId = contactId;
 		this.mailboxPropertiesUpdate = mailboxPropertiesUpdate;
 	}
@@ -29,7 +27,6 @@ public class RemoteMailboxPropertiesUpdateEvent extends Event {
 		return contactId;
 	}
 
-	@Nullable
 	public MailboxPropertiesUpdate getMailboxPropertiesUpdate() {
 		return mailboxPropertiesUpdate;
 	}

bramble-api/src/test/java/org/briarproject/bramble/test/TestUtils.java

@@ -22,6 +22,7 @@ import org.briarproject.bramble.api.identity.Identity;
 import org.briarproject.bramble.api.identity.LocalAuthor;
 import org.briarproject.bramble.api.mailbox.MailboxProperties;
 import org.briarproject.bramble.api.mailbox.MailboxPropertiesUpdate;
+import org.briarproject.bramble.api.mailbox.MailboxPropertiesUpdateMailbox;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.sync.ClientId;
@@ -286,10 +287,21 @@ public class TestUtils {
 		if (a == null || b == null) {
 			return a == b;
 		}
-		return a.getOnion().equals(b.getOnion()) &&
+		if (!a.hasMailbox() && !b.hasMailbox()) {
-				a.getAuthToken().equals(b.getAuthToken()) &&
+			return a.getClientSupports().equals(b.getClientSupports());
-				a.getInboxId().equals(b.getInboxId()) &&
+		} else if (a.hasMailbox() && b.hasMailbox()) {
-				a.getOutboxId().equals(b.getOutboxId());
+			MailboxPropertiesUpdateMailbox am =
+					(MailboxPropertiesUpdateMailbox) a;
+			MailboxPropertiesUpdateMailbox bm =
+					(MailboxPropertiesUpdateMailbox) b;
+			return am.getClientSupports().equals(bm.getClientSupports()) &&
+					am.getServerSupports().equals(bm.getServerSupports()) &&
+					am.getOnion().equals(bm.getOnion()) &&
+					am.getAuthToken().equals(bm.getAuthToken()) &&
+					am.getInboxId().equals(bm.getInboxId()) &&
+					am.getOutboxId().equals(bm.getOutboxId());
+		}
+		return false;
 	}
 
 	public static boolean mailboxPropertiesEqual(

bramble-core/src/main/java/org/briarproject/bramble/client/ClientHelperImpl.java

@@ -26,6 +26,8 @@ import org.briarproject.bramble.api.identity.AuthorFactory;
 import org.briarproject.bramble.api.mailbox.MailboxAuthToken;
 import org.briarproject.bramble.api.mailbox.MailboxFolderId;
 import org.briarproject.bramble.api.mailbox.MailboxPropertiesUpdate;
+import org.briarproject.bramble.api.mailbox.MailboxPropertiesUpdateMailbox;
+import org.briarproject.bramble.api.mailbox.MailboxVersion;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.properties.TransportProperties;
@@ -39,12 +41,13 @@ import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.security.GeneralSecurityException;
+import java.util.ArrayList;
 import java.util.Collection;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
 
-import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
@@ -412,11 +415,28 @@ class ClientHelperImpl implements ClientHelper {
 	}
 
 	@Override
-	@Nullable
 	public MailboxPropertiesUpdate parseAndValidateMailboxPropertiesUpdate(
+			BdfList clientSupports, BdfList serverSupports,
 			BdfDictionary properties) throws FormatException {
+		List<MailboxVersion> clientSupportsList =
+				getMailboxVersionList(clientSupports);
+		List<MailboxVersion> serverSupportsList =
+				getMailboxVersionList(serverSupports);
+
+		// We must always learn what Mailbox API version(s) the client supports
+		if (clientSupports.isEmpty()) {
+			throw new FormatException();
+		}
 		if (properties.isEmpty()) {
-			return null;
+			// No mailbox -- cannot claim to support any API versions!
+			if (!serverSupports.isEmpty()) {
+				throw new FormatException();
+			}
+			return new MailboxPropertiesUpdate(clientSupportsList);
+		}
+		// Mailbox must be accompanied by the Mailbox API version(s) it supports
+		if (serverSupports.isEmpty()) {
+			throw new FormatException();
 		}
 		// Accepting more props than we need, for forward compatibility
 		if (properties.size() < PROP_COUNT) {
@@ -435,9 +455,23 @@ class ClientHelperImpl implements ClientHelper {
 		checkLength(inboxId, UniqueId.LENGTH);
 		byte[] outboxId = properties.getRaw(PROP_KEY_OUTBOXID);
 		checkLength(outboxId, UniqueId.LENGTH);
-		return new MailboxPropertiesUpdate(onion,
+		return new MailboxPropertiesUpdateMailbox(clientSupportsList,
-				new MailboxAuthToken(authToken), new MailboxFolderId(inboxId),
+				serverSupportsList, onion, new MailboxAuthToken(authToken),
-				new MailboxFolderId(outboxId));
+				new MailboxFolderId(inboxId), new MailboxFolderId(outboxId));
+	}
+
+	private List<MailboxVersion> getMailboxVersionList(BdfList bdfList)
+			throws FormatException {
+		List<MailboxVersion> list = new ArrayList<>();
+		for (int i = 0; i < bdfList.size(); i++) {
+			BdfList element = bdfList.getList(i);
+			if (element.size() != 2) {
+				throw new FormatException();
+			}
+			list.add(new MailboxVersion(element.getLong(0).intValue(),
+					element.getLong(1).intValue()));
+		}
+		return list;
 	}
 
 	@Override

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxApi.java

@@ -7,6 +7,8 @@ import org.briarproject.bramble.api.mailbox.MailboxAuthToken;
 import org.briarproject.bramble.api.mailbox.MailboxFileId;
 import org.briarproject.bramble.api.mailbox.MailboxFolderId;
 import org.briarproject.bramble.api.mailbox.MailboxProperties;
+import org.briarproject.bramble.api.mailbox.MailboxPropertyManager;
+import org.briarproject.bramble.api.mailbox.MailboxVersion;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
 import java.io.File;
@@ -17,9 +19,18 @@ import java.util.List;
 import javax.annotation.Nonnull;
 import javax.annotation.concurrent.Immutable;
 
+import static java.util.Collections.singletonList;
+
 @NotNullByDefault
 interface MailboxApi {
 
+	/**
+	 * Mailbox API versions that we support as a client. This is reported to our
+	 * contacts by {@link MailboxPropertyManager}.
+	 */
+	List<MailboxVersion> CLIENT_SUPPORTS = singletonList(
+			new MailboxVersion(1, 0));
+
 	/**
 	 * Sets up the mailbox with the setup token.
 	 *

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxPairingTaskImpl.java

@@ -127,7 +127,7 @@ class MailboxPairingTaskImpl implements MailboxPairingTask {
 			for (Contact c : db.getContacts(txn)) {
 				MailboxPropertiesUpdate remoteProps = mailboxPropertyManager
 						.getRemoteProperties(txn, c.getId());
-				if (remoteProps == null) {
+				if (remoteProps == null || !remoteProps.hasMailbox()) {
 					db.resetUnackedMessagesToSend(txn, c.getId());
 				}
 			}

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxPropertyManagerImpl.java

@@ -19,9 +19,11 @@ import org.briarproject.bramble.api.mailbox.MailboxAuthToken;
 import org.briarproject.bramble.api.mailbox.MailboxFolderId;
 import org.briarproject.bramble.api.mailbox.MailboxProperties;
 import org.briarproject.bramble.api.mailbox.MailboxPropertiesUpdate;
+import org.briarproject.bramble.api.mailbox.MailboxPropertiesUpdateMailbox;
 import org.briarproject.bramble.api.mailbox.MailboxPropertyManager;
 import org.briarproject.bramble.api.mailbox.MailboxSettingsManager;
 import org.briarproject.bramble.api.mailbox.MailboxSettingsManager.MailboxHook;
+import org.briarproject.bramble.api.mailbox.MailboxVersion;
 import org.briarproject.bramble.api.mailbox.RemoteMailboxPropertiesUpdateEvent;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.Group;
@@ -35,6 +37,7 @@ import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.api.versioning.ClientVersioningManager;
 import org.briarproject.bramble.api.versioning.ClientVersioningManager.ClientVersioningHook;
 
+import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
 
@@ -42,6 +45,7 @@ import javax.annotation.Nullable;
 import javax.inject.Inject;
 
 import static org.briarproject.bramble.api.sync.validation.IncomingMessageHook.DeliveryAction.ACCEPT_DO_NOT_SHARE;
+import static org.briarproject.bramble.mailbox.MailboxApi.CLIENT_SUPPORTS;
 
 @NotNullByDefault
 class MailboxPropertyManagerImpl implements MailboxPropertyManager,
@@ -100,11 +104,15 @@ class MailboxPropertyManagerImpl implements MailboxPropertyManager,
 		db.setGroupVisibility(txn, c.getId(), g.getId(), client);
 		// Attach the contact ID to the group
 		clientHelper.setContactId(txn, g.getId(), c.getId());
-		// If we are paired, create and send props to the newly added contact
 		MailboxProperties ownProps =
 				mailboxSettingsManager.getOwnMailboxProperties(txn);
 		if (ownProps != null) {
-			createAndSendProperties(txn, c, ownProps.getOnion());
+			// We are paired, create and send props to the newly added contact
+			createAndSendProperties(txn, c, ownProps.getServerSupports(),
+					ownProps.getOnion());
+		} else {
+			// Not paired, but we still want to get our clientSupports sent
+			sendEmptyProperties(txn, c);
 		}
 	}
 
@@ -114,10 +122,11 @@ class MailboxPropertyManagerImpl implements MailboxPropertyManager,
 	}
 
 	@Override
-	public void mailboxPaired(Transaction txn, String ownOnion)
+	public void mailboxPaired(Transaction txn, String ownOnion,
+			List<MailboxVersion> serverSupports)
 			throws DbException {
 		for (Contact c : db.getContacts(txn)) {
-			createAndSendProperties(txn, c, ownOnion);
+			createAndSendProperties(txn, c, serverSupports, ownOnion);
 		}
 	}
 
@@ -186,12 +195,15 @@ class MailboxPropertyManagerImpl implements MailboxPropertyManager,
 
 	/**
 	 * Creates and sends an update message to the given contact. The message
-	 * holds our own mailbox's onion, and generated unique properties. All of
+	 * holds our own mailbox's onion, generated unique properties, and lists of
-	 * which the contact needs to communicate with our Mailbox.
+	 * supported Mailbox API version(s). All of which the contact needs to
+	 * communicate with our Mailbox.
 	 */
-	private void createAndSendProperties(Transaction txn,
+	private void createAndSendProperties(Transaction txn, Contact c,
-			Contact c, String ownOnion) throws DbException {
+			List<MailboxVersion> serverSupports, String ownOnion)
-		MailboxPropertiesUpdate p = new MailboxPropertiesUpdate(ownOnion,
+			throws DbException {
+		MailboxPropertiesUpdate p = new MailboxPropertiesUpdateMailbox(
+				CLIENT_SUPPORTS, serverSupports, ownOnion,
 				new MailboxAuthToken(crypto.generateUniqueId().getBytes()),
 				new MailboxFolderId(crypto.generateUniqueId().getBytes()),
 				new MailboxFolderId(crypto.generateUniqueId().getBytes()));
@@ -200,14 +212,17 @@ class MailboxPropertyManagerImpl implements MailboxPropertyManager,
 	}
 
 	/**
-	 * Sends an empty update message to the given contact. The empty update
+	 * Sends an update message with empty properties to the given contact. The
-	 * indicates for the receiving contact that we no longer have a Mailbox that
+	 * empty update indicates for the receiving contact that we don't have any
-	 * they can use.
+	 * Mailbox that they can use. It still includes the list of Mailbox API
+	 * version(s) that we support as a client.
 	 */
 	private void sendEmptyProperties(Transaction txn, Contact c)
 			throws DbException {
 		Group g = getContactGroup(c);
-		storeMessageReplaceLatest(txn, g.getId(), null);
+		MailboxPropertiesUpdate p =
+				new MailboxPropertiesUpdate(CLIENT_SUPPORTS);
+		storeMessageReplaceLatest(txn, g.getId(), p);
 	}
 
 	@Nullable
@@ -229,7 +244,7 @@ class MailboxPropertyManagerImpl implements MailboxPropertyManager,
 	}
 
 	private void storeMessageReplaceLatest(Transaction txn, GroupId g,
-			@Nullable MailboxPropertiesUpdate p) throws DbException {
+			MailboxPropertiesUpdate p) throws DbException {
 		try {
 			LatestUpdate latest = findLatest(txn, g, true);
 			long version = latest == null ? 1 : latest.version + 1;
@@ -266,23 +281,38 @@ class MailboxPropertyManagerImpl implements MailboxPropertyManager,
 		return null;
 	}
 
-	private BdfList encodeProperties(long version,
+	private BdfList encodeProperties(long version, MailboxPropertiesUpdate p) {
-			@Nullable MailboxPropertiesUpdate p) {
 		BdfDictionary dict = new BdfDictionary();
-		if (p != null) {
+		BdfList serverSupports = new BdfList();
-			dict.put(PROP_KEY_ONION, p.getOnion());
+		if (p.hasMailbox()) {
-			dict.put(PROP_KEY_AUTHTOKEN, p.getAuthToken().getBytes());
+			MailboxPropertiesUpdateMailbox pm =
-			dict.put(PROP_KEY_INBOXID, p.getInboxId().getBytes());
+					(MailboxPropertiesUpdateMailbox) p;
-			dict.put(PROP_KEY_OUTBOXID, p.getOutboxId().getBytes());
+			serverSupports = encodeSupportsList(pm.getServerSupports());
+			dict.put(PROP_KEY_ONION, pm.getOnion());
+			dict.put(PROP_KEY_AUTHTOKEN, pm.getAuthToken().getBytes());
+			dict.put(PROP_KEY_INBOXID, pm.getInboxId().getBytes());
+			dict.put(PROP_KEY_OUTBOXID, pm.getOutboxId().getBytes());
 		}
-		return BdfList.of(version, dict);
+		return BdfList.of(version, encodeSupportsList(p.getClientSupports()),
+				serverSupports, dict);
+	}
+
+	private BdfList encodeSupportsList(List<MailboxVersion> supportsList) {
+		BdfList supports = new BdfList();
+		for (MailboxVersion version : supportsList) {
+			supports.add(BdfList.of(version.getMajor(), version.getMinor()));
+		}
+		return supports;
 	}
 
-	@Nullable
 	private MailboxPropertiesUpdate parseProperties(BdfList body)
 			throws FormatException {
-		BdfDictionary dict = body.getDictionary(1);
+		BdfList clientSupports = body.getList(1);
-		return clientHelper.parseAndValidateMailboxPropertiesUpdate(dict);
+		BdfList serverSupports = body.getList(2);
+		BdfDictionary dict = body.getDictionary(3);
+		return clientHelper.parseAndValidateMailboxPropertiesUpdate(
+				clientSupports, serverSupports, dict
+		);
 	}
 
 	private Group getContactGroup(Contact c) {

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxPropertyValidator.java

@@ -31,14 +31,20 @@ class MailboxPropertyValidator extends BdfMessageValidator {
 	@Override
 	protected BdfMessageContext validateMessage(Message m, Group g,
 			BdfList body) throws InvalidMessageException, FormatException {
-		// Version, properties
+		// Version, Properties, clientSupports, serverSupports
-		checkSize(body, 2);
+		checkSize(body, 4);
 		// Version
 		long version = body.getLong(0);
 		if (version < 0) throw new FormatException();
+		// clientSupports
+		BdfList clientSupports = body.getList(1);
+		// serverSupports
+		BdfList serverSupports = body.getList(2);
 		// Properties
-		BdfDictionary dictionary = body.getDictionary(1);
+		BdfDictionary dictionary = body.getDictionary(3);
-		clientHelper.parseAndValidateMailboxPropertiesUpdate(dictionary);
+		clientHelper.parseAndValidateMailboxPropertiesUpdate(clientSupports,
+				serverSupports, dictionary
+		);
 		// Return the metadata
 		BdfDictionary meta = new BdfDictionary();
 		meta.put(MSG_KEY_VERSION, version);

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxSettingsManagerImpl.java

@@ -91,7 +91,7 @@ class MailboxSettingsManagerImpl implements MailboxSettingsManager {
 		s.putIntArray(SETTINGS_KEY_SERVER_SUPPORTS, ints);
 		settingsManager.mergeSettings(txn, s, SETTINGS_NAMESPACE);
 		for (MailboxHook hook : hooks) {
-			hook.mailboxPaired(txn, p.getOnion());
+			hook.mailboxPaired(txn, p.getOnion(), p.getServerSupports());
 		}
 	}
 

bramble-core/src/test/java/org/briarproject/bramble/client/ClientHelperImplTest.java

@@ -24,6 +24,8 @@ import org.briarproject.bramble.api.identity.AuthorFactory;
 import org.briarproject.bramble.api.mailbox.MailboxAuthToken;
 import org.briarproject.bramble.api.mailbox.MailboxFolderId;
 import org.briarproject.bramble.api.mailbox.MailboxPropertiesUpdate;
+import org.briarproject.bramble.api.mailbox.MailboxPropertiesUpdateMailbox;
+import org.briarproject.bramble.api.mailbox.MailboxVersion;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageFactory;
@@ -41,6 +43,7 @@ import java.util.HashMap;
 import java.util.Map;
 import java.util.Random;
 
+import static java.util.Collections.singletonList;
 import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_AUTHOR_NAME_LENGTH;
 import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_PUBLIC_KEY_LENGTH;
 import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_SIGNATURE_LENGTH;
@@ -58,7 +61,7 @@ import static org.briarproject.bramble.test.TestUtils.mailboxPropertiesUpdateEqu
 import static org.briarproject.bramble.util.StringUtils.getRandomString;
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 
@@ -95,10 +98,20 @@ public class ClientHelperImplTest extends BrambleMockTestCase {
 			messageFactory, bdfReaderFactory, bdfWriterFactory, metadataParser,
 			metadataEncoder, cryptoComponent, authorFactory);
 
-	private final MailboxPropertiesUpdate validMailboxPropsUpdate;
+	private final MailboxPropertiesUpdateMailbox validMailboxPropsUpdate;
+	private final BdfList emptyClientSupports;
+	private final BdfList someClientSupports;
+	private final BdfList emptyServerSupports;
+	private final BdfList someServerSupports;
 
 	public ClientHelperImplTest() {
-		validMailboxPropsUpdate = new MailboxPropertiesUpdate(
+		emptyClientSupports = new BdfList();
+		someClientSupports = BdfList.of(BdfList.of(1, 0));
+		emptyServerSupports = new BdfList();
+		someServerSupports = BdfList.of(BdfList.of(1, 0));
+		validMailboxPropsUpdate = new MailboxPropertiesUpdateMailbox(
+				singletonList(new MailboxVersion(1, 0)),
+				singletonList(new MailboxVersion(1, 0)),
 				"pg6mmjiyjmcrsslvykfwnntlaru7p5svn6y2ymmju6nubxndf4pscryd",
 				new MailboxAuthToken(getRandomId()),
 				new MailboxFolderId(getRandomId()),
@@ -546,23 +559,84 @@ public class ClientHelperImplTest extends BrambleMockTestCase {
 		}});
 	}
 
+	@Test(expected = FormatException.class)
+	public void testRejectsMailboxPropsWithEmptyClientSupports()
+			throws Exception {
+		BdfDictionary emptyPropsDict = new BdfDictionary();
+		clientHelper.parseAndValidateMailboxPropertiesUpdate(
+				emptyClientSupports, emptyServerSupports, emptyPropsDict
+		);
+	}
+
 	@Test
 	public void testParseEmptyMailboxPropsUpdate() throws Exception {
 		BdfDictionary emptyPropsDict = new BdfDictionary();
 		MailboxPropertiesUpdate parsedProps = clientHelper
-				.parseAndValidateMailboxPropertiesUpdate(emptyPropsDict);
+				.parseAndValidateMailboxPropertiesUpdate(someClientSupports,
-		assertNull(parsedProps);
+						emptyServerSupports, emptyPropsDict
+				);
+		assertFalse(parsedProps.hasMailbox());
+	}
+
+	@Test(expected = FormatException.class)
+	public void testRejectsEmptyMailboxPropsWithSomeServerSupports()
+			throws Exception {
+		BdfDictionary emptyPropsDict = new BdfDictionary();
+		clientHelper.parseAndValidateMailboxPropertiesUpdate(someClientSupports,
+				someServerSupports, emptyPropsDict
+		);
+	}
+
+	@Test(expected = FormatException.class)
+	public void testRejectsMailboxPropsShortSupports() throws Exception {
+		clientHelper.parseAndValidateMailboxPropertiesUpdate(
+				BdfList.of(BdfList.of(1)), emptyServerSupports,
+				new BdfDictionary()
+		);
+	}
+
+	@Test(expected = FormatException.class)
+	public void testRejectsMailboxPropsLongSupports() throws Exception {
+		clientHelper.parseAndValidateMailboxPropertiesUpdate(
+				BdfList.of(BdfList.of(1, 0, 0)), emptyServerSupports,
+				new BdfDictionary()
+		);
+	}
+
+	@Test(expected = FormatException.class)
+	public void testRejectsMailboxPropsNonIntSupports() throws Exception {
+		clientHelper.parseAndValidateMailboxPropertiesUpdate(
+				BdfList.of(BdfList.of(1, "0")), emptyServerSupports,
+				new BdfDictionary()
+		);
+	}
+
+	@Test(expected = FormatException.class)
+	public void testRejectsMailboxPropsNonListSupports() throws Exception {
+		clientHelper.parseAndValidateMailboxPropertiesUpdate(
+				BdfList.of("non-list"), emptyServerSupports, new BdfDictionary()
+		);
 	}
 
 	@Test
 	public void testParseValidMailboxPropsUpdate() throws Exception {
 		MailboxPropertiesUpdate parsedProps = clientHelper
 				.parseAndValidateMailboxPropertiesUpdate(
-						getValidMailboxPropsUpdateDict());
+						someClientSupports, someServerSupports,
+						getValidMailboxPropsUpdateDict()
+				);
 		assertTrue(mailboxPropertiesUpdateEqual(validMailboxPropsUpdate,
 				parsedProps));
 	}
 
+	@Test(expected = FormatException.class)
+	public void rejectsMailboxPropsWithEmptyServerSupports() throws Exception {
+		clientHelper.parseAndValidateMailboxPropertiesUpdate(
+				someClientSupports, emptyServerSupports,
+				getValidMailboxPropsUpdateDict()
+		);
+	}
+
 	@Test(expected = FormatException.class)
 	public void testRejectsMailboxPropsUpdateOnionNotDecodable()
 			throws Exception {
@@ -570,7 +644,9 @@ public class ClientHelperImplTest extends BrambleMockTestCase {
 		String badOnion = "!" + propsDict.getString(PROP_KEY_ONION)
 				.substring(1);
 		propsDict.put(PROP_KEY_ONION, badOnion);
-		clientHelper.parseAndValidateMailboxPropertiesUpdate(propsDict);
+		clientHelper.parseAndValidateMailboxPropertiesUpdate(someClientSupports,
+				emptyServerSupports, propsDict
+		);
 	}
 
 	@Test(expected = FormatException.class)
@@ -579,7 +655,9 @@ public class ClientHelperImplTest extends BrambleMockTestCase {
 		BdfDictionary propsDict = getValidMailboxPropsUpdateDict();
 		String tooLongOnion = propsDict.getString(PROP_KEY_ONION) + "!";
 		propsDict.put(PROP_KEY_ONION, tooLongOnion);
-		clientHelper.parseAndValidateMailboxPropertiesUpdate(propsDict);
+		clientHelper.parseAndValidateMailboxPropertiesUpdate(someClientSupports,
+				emptyServerSupports, propsDict
+		);
 	}
 
 	@Test(expected = FormatException.class)
@@ -587,7 +665,9 @@ public class ClientHelperImplTest extends BrambleMockTestCase {
 			throws Exception {
 		BdfDictionary propsDict = getValidMailboxPropsUpdateDict();
 		propsDict.put(PROP_KEY_INBOXID, getRandomBytes(UniqueId.LENGTH + 1));
-		clientHelper.parseAndValidateMailboxPropertiesUpdate(propsDict);
+		clientHelper.parseAndValidateMailboxPropertiesUpdate(someClientSupports,
+				someServerSupports, propsDict
+		);
 	}
 
 	@Test(expected = FormatException.class)
@@ -595,7 +675,9 @@ public class ClientHelperImplTest extends BrambleMockTestCase {
 			throws Exception {
 		BdfDictionary propsDict = getValidMailboxPropsUpdateDict();
 		propsDict.put(PROP_KEY_OUTBOXID, getRandomBytes(UniqueId.LENGTH + 1));
-		clientHelper.parseAndValidateMailboxPropertiesUpdate(propsDict);
+		clientHelper.parseAndValidateMailboxPropertiesUpdate(someClientSupports,
+				someServerSupports, propsDict
+		);
 	}
 
 	@Test(expected = FormatException.class)
@@ -603,14 +685,18 @@ public class ClientHelperImplTest extends BrambleMockTestCase {
 			throws Exception {
 		BdfDictionary propsDict = getValidMailboxPropsUpdateDict();
 		propsDict.put(PROP_KEY_AUTHTOKEN, getRandomBytes(UniqueId.LENGTH + 1));
-		clientHelper.parseAndValidateMailboxPropertiesUpdate(propsDict);
+		clientHelper.parseAndValidateMailboxPropertiesUpdate(someClientSupports,
+				someServerSupports, propsDict
+		);
 	}
 
 	@Test(expected = FormatException.class)
 	public void testRejectsMailboxPropsUpdateMissingOnion() throws Exception {
 		BdfDictionary propsDict = getValidMailboxPropsUpdateDict();
 		propsDict.remove(PROP_KEY_ONION);
-		clientHelper.parseAndValidateMailboxPropertiesUpdate(propsDict);
+		clientHelper.parseAndValidateMailboxPropertiesUpdate(someClientSupports,
+				someServerSupports, propsDict
+		);
 	}
 
 	@Test(expected = FormatException.class)
@@ -618,14 +704,18 @@ public class ClientHelperImplTest extends BrambleMockTestCase {
 			throws Exception {
 		BdfDictionary propsDict = getValidMailboxPropsUpdateDict();
 		propsDict.remove(PROP_KEY_AUTHTOKEN);
-		clientHelper.parseAndValidateMailboxPropertiesUpdate(propsDict);
+		clientHelper.parseAndValidateMailboxPropertiesUpdate(someClientSupports,
+				someServerSupports, propsDict
+		);
 	}
 
 	@Test(expected = FormatException.class)
 	public void testRejectsMailboxPropsUpdateMissingInboxId() throws Exception {
 		BdfDictionary propsDict = getValidMailboxPropsUpdateDict();
 		propsDict.remove(PROP_KEY_INBOXID);
-		clientHelper.parseAndValidateMailboxPropertiesUpdate(propsDict);
+		clientHelper.parseAndValidateMailboxPropertiesUpdate(someClientSupports,
+				someServerSupports, propsDict
+		);
 	}
 
 	@Test(expected = FormatException.class)
@@ -633,7 +723,9 @@ public class ClientHelperImplTest extends BrambleMockTestCase {
 			throws Exception {
 		BdfDictionary propsDict = getValidMailboxPropsUpdateDict();
 		propsDict.remove(PROP_KEY_OUTBOXID);
-		clientHelper.parseAndValidateMailboxPropertiesUpdate(propsDict);
+		clientHelper.parseAndValidateMailboxPropertiesUpdate(someClientSupports,
+				someServerSupports, propsDict
+		);
 	}
 
 }

bramble-core/src/test/java/org/briarproject/bramble/mailbox/MailboxPairingTaskImplTest.java

@@ -9,6 +9,7 @@ import org.briarproject.bramble.api.mailbox.MailboxAuthToken;
 import org.briarproject.bramble.api.mailbox.MailboxPairingState;
 import org.briarproject.bramble.api.mailbox.MailboxPairingTask;
 import org.briarproject.bramble.api.mailbox.MailboxProperties;
+import org.briarproject.bramble.api.mailbox.MailboxPropertiesUpdate;
 import org.briarproject.bramble.api.mailbox.MailboxPropertyManager;
 import org.briarproject.bramble.api.mailbox.MailboxSettingsManager;
 import org.briarproject.bramble.api.mailbox.OwnMailboxConnectionStatusEvent;
@@ -24,10 +25,11 @@ import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.nio.charset.Charset;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.concurrent.Executor;
 import java.util.concurrent.atomic.AtomicInteger;
 
+import static java.util.Collections.singletonList;
+import static org.briarproject.bramble.mailbox.MailboxApi.CLIENT_SUPPORTS;
 import static org.briarproject.bramble.test.TestUtils.getContact;
 import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
 import static org.briarproject.bramble.test.TestUtils.getRandomId;
@@ -105,16 +107,18 @@ public class MailboxPairingTaskImplTest extends BrambleMockTestCase {
 		}});
 		Contact contact1 = getContact();
 		Transaction txn = new Transaction(null, false);
+		MailboxPropertiesUpdate emptyProps = new MailboxPropertiesUpdate(
+				CLIENT_SUPPORTS);
 		context.checking(new DbExpectations() {{
 			oneOf(db).transaction(with(false), withDbRunnable(txn));
 			oneOf(mailboxSettingsManager).setOwnMailboxProperties(
 					with(txn), with(matches(ownerProperties)));
 			oneOf(mailboxSettingsManager).recordSuccessfulConnection(txn, time);
 			oneOf(db).getContacts(txn);
-			will(returnValue(Collections.singletonList(contact1)));
+			will(returnValue(singletonList(contact1)));
 			oneOf(mailboxPropertyManager).getRemoteProperties(txn,
 					contact1.getId());
-			will(returnValue(null));
+			will(returnValue(emptyProps));
 			oneOf(db).resetUnackedMessagesToSend(txn, contact1.getId());
 		}});
 

bramble-core/src/test/java/org/briarproject/bramble/mailbox/MailboxPropertyManagerImplTest.java

@@ -15,7 +15,9 @@ import org.briarproject.bramble.api.mailbox.MailboxAuthToken;
 import org.briarproject.bramble.api.mailbox.MailboxFolderId;
 import org.briarproject.bramble.api.mailbox.MailboxProperties;
 import org.briarproject.bramble.api.mailbox.MailboxPropertiesUpdate;
+import org.briarproject.bramble.api.mailbox.MailboxPropertiesUpdateMailbox;
 import org.briarproject.bramble.api.mailbox.MailboxSettingsManager;
+import org.briarproject.bramble.api.mailbox.MailboxVersion;
 import org.briarproject.bramble.api.mailbox.RemoteMailboxPropertiesUpdateEvent;
 import org.briarproject.bramble.api.sync.Group;
 import org.briarproject.bramble.api.sync.GroupId;
@@ -27,7 +29,6 @@ import org.briarproject.bramble.test.BrambleMockTestCase;
 import org.jmock.Expectations;
 import org.junit.Test;
 
-import java.util.ArrayList;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
@@ -43,6 +44,7 @@ import static org.briarproject.bramble.api.mailbox.MailboxPropertyManager.PROP_K
 import static org.briarproject.bramble.api.mailbox.MailboxPropertyManager.PROP_KEY_OUTBOXID;
 import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
 import static org.briarproject.bramble.api.sync.validation.IncomingMessageHook.DeliveryAction.ACCEPT_DO_NOT_SHARE;
+import static org.briarproject.bramble.mailbox.MailboxApi.CLIENT_SUPPORTS;
 import static org.briarproject.bramble.test.TestUtils.getContact;
 import static org.briarproject.bramble.test.TestUtils.getGroup;
 import static org.briarproject.bramble.test.TestUtils.getMessage;
@@ -72,21 +74,44 @@ public class MailboxPropertyManagerImplTest extends BrambleMockTestCase {
 	private final Group localGroup = getGroup(CLIENT_ID, MAJOR_VERSION);
 	private final BdfDictionary propsDict;
 	private final BdfDictionary emptyPropsDict = new BdfDictionary();
-	private final MailboxPropertiesUpdate props;
+	private final BdfList realClientSupports;
+	private final BdfList someClientSupports;
+	private final List<MailboxVersion> someClientSupportsList;
+	private final BdfList emptyServerSupports;
+	private final BdfList someServerSupports;
+	private final List<MailboxVersion> someServerSupportsList;
+	private final MailboxPropertiesUpdateMailbox updateMailbox;
+	private final MailboxPropertiesUpdate updateNoMailbox;
 	private final MailboxProperties ownProps;
 
 	public MailboxPropertyManagerImplTest() {
+		someClientSupports = BdfList.of(BdfList.of(1, 0));
+		someClientSupportsList = singletonList(new MailboxVersion(1, 0));
+		emptyServerSupports = new BdfList();
+		someServerSupports = BdfList.of(BdfList.of(1, 0));
+		someServerSupportsList = singletonList(new MailboxVersion(1, 0));
+		realClientSupports = new BdfList();
+		for (MailboxVersion v : CLIENT_SUPPORTS) {
+			realClientSupports.add(BdfList.of(v.getMajor(), v.getMinor()));
+		}
 		ownProps = new MailboxProperties("http://bar.onion",
-				new MailboxAuthToken(getRandomId()), true, new ArrayList<>());
+				new MailboxAuthToken(getRandomId()), true,
-		props = new MailboxPropertiesUpdate(ownProps.getOnion(),
+				someServerSupportsList);
+		updateMailbox = new MailboxPropertiesUpdateMailbox(
+				singletonList(new MailboxVersion(1, 0)),
+				singletonList(new MailboxVersion(1, 0)),
+				ownProps.getOnion(),
 				new MailboxAuthToken(getRandomId()),
 				new MailboxFolderId(getRandomId()),
 				new MailboxFolderId(getRandomId()));
 		propsDict = new BdfDictionary();
-		propsDict.put(PROP_KEY_ONION, props.getOnion());
+		propsDict.put(PROP_KEY_ONION, updateMailbox.getOnion());
-		propsDict.put(PROP_KEY_AUTHTOKEN, props.getAuthToken().getBytes());
+		propsDict.put(PROP_KEY_AUTHTOKEN,
-		propsDict.put(PROP_KEY_INBOXID, props.getInboxId().getBytes());
+				updateMailbox.getAuthToken().getBytes());
-		propsDict.put(PROP_KEY_OUTBOXID, props.getOutboxId().getBytes());
+		propsDict.put(PROP_KEY_INBOXID, updateMailbox.getInboxId().getBytes());
+		propsDict.put(PROP_KEY_OUTBOXID,
+				updateMailbox.getOutboxId().getBytes());
+		updateNoMailbox = new MailboxPropertiesUpdate(someClientSupportsList);
 	}
 
 	private MailboxPropertyManagerImpl createInstance() {
@@ -105,6 +130,7 @@ public class MailboxPropertyManagerImplTest extends BrambleMockTestCase {
 		Transaction txn = new Transaction(null, false);
 		Contact contact = getContact();
 		Group contactGroup = getGroup(CLIENT_ID, MAJOR_VERSION);
+		Map<MessageId, BdfDictionary> messageMetadata = new LinkedHashMap<>();
 
 		context.checking(new Expectations() {{
 			oneOf(db).containsGroup(txn, localGroup.getId());
@@ -125,6 +151,14 @@ public class MailboxPropertyManagerImplTest extends BrambleMockTestCase {
 					contact.getId());
 			oneOf(mailboxSettingsManager).getOwnMailboxProperties(txn);
 			will(returnValue(null));
+			oneOf(contactGroupFactory).createContactGroup(CLIENT_ID,
+					MAJOR_VERSION, contact);
+			will(returnValue(contactGroup));
+			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
+					contactGroup.getId());
+			will(returnValue(messageMetadata));
+			expectStoreMessage(txn, contactGroup.getId(), 1, realClientSupports,
+					emptyServerSupports, emptyPropsDict, true);
 		}});
 
 		MailboxPropertyManagerImpl t = createInstance();
@@ -159,18 +193,19 @@ public class MailboxPropertyManagerImplTest extends BrambleMockTestCase {
 			oneOf(mailboxSettingsManager).getOwnMailboxProperties(txn);
 			will(returnValue(ownProps));
 			oneOf(crypto).generateUniqueId();
-			will(returnValue(props.getAuthToken()));
+			will(returnValue(updateMailbox.getAuthToken()));
 			oneOf(crypto).generateUniqueId();
-			will(returnValue(props.getInboxId()));
+			will(returnValue(updateMailbox.getInboxId()));
 			oneOf(crypto).generateUniqueId();
-			will(returnValue(props.getOutboxId()));
+			will(returnValue(updateMailbox.getOutboxId()));
 			oneOf(contactGroupFactory).createContactGroup(CLIENT_ID,
 					MAJOR_VERSION, contact);
 			will(returnValue(contactGroup));
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					contactGroup.getId());
 			will(returnValue(messageMetadata));
-			expectStoreMessage(txn, contactGroup.getId(), propsDict, 1, true);
+			expectStoreMessage(txn, contactGroup.getId(), 1, realClientSupports,
+					someServerSupports, propsDict, true);
 		}});
 
 		MailboxPropertyManagerImpl t = createInstance();
@@ -197,6 +232,7 @@ public class MailboxPropertyManagerImplTest extends BrambleMockTestCase {
 		Transaction txn = new Transaction(null, false);
 		Contact contact = getContact();
 		Group contactGroup = getGroup(CLIENT_ID, MAJOR_VERSION);
+		Map<MessageId, BdfDictionary> messageMetadata = new LinkedHashMap<>();
 
 		context.checking(new Expectations() {{
 			// Create the group and share it with the contact
@@ -213,6 +249,14 @@ public class MailboxPropertyManagerImplTest extends BrambleMockTestCase {
 					contact.getId());
 			oneOf(mailboxSettingsManager).getOwnMailboxProperties(txn);
 			will(returnValue(null));
+			oneOf(contactGroupFactory).createContactGroup(CLIENT_ID,
+					MAJOR_VERSION, contact);
+			will(returnValue(contactGroup));
+			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
+					contactGroup.getId());
+			will(returnValue(messageMetadata));
+			expectStoreMessage(txn, contactGroup.getId(), 1, realClientSupports,
+					emptyServerSupports, emptyPropsDict, true);
 		}});
 
 		MailboxPropertyManagerImpl t = createInstance();
@@ -243,18 +287,19 @@ public class MailboxPropertyManagerImplTest extends BrambleMockTestCase {
 			oneOf(mailboxSettingsManager).getOwnMailboxProperties(txn);
 			will(returnValue(ownProps));
 			oneOf(crypto).generateUniqueId();
-			will(returnValue(props.getAuthToken()));
+			will(returnValue(updateMailbox.getAuthToken()));
 			oneOf(crypto).generateUniqueId();
-			will(returnValue(props.getInboxId()));
+			will(returnValue(updateMailbox.getInboxId()));
 			oneOf(crypto).generateUniqueId();
-			will(returnValue(props.getOutboxId()));
+			will(returnValue(updateMailbox.getOutboxId()));
 			oneOf(contactGroupFactory).createContactGroup(CLIENT_ID,
 					MAJOR_VERSION, contact);
 			will(returnValue(contactGroup));
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					contactGroup.getId());
 			will(returnValue(messageMetadata));
-			expectStoreMessage(txn, contactGroup.getId(), propsDict, 1, true);
+			expectStoreMessage(txn, contactGroup.getId(), 1, someClientSupports,
+					someServerSupports, propsDict, true);
 		}});
 
 		MailboxPropertyManagerImpl t = createInstance();
@@ -285,7 +330,8 @@ public class MailboxPropertyManagerImplTest extends BrambleMockTestCase {
 		Contact contact = getContact();
 		GroupId contactGroupId = new GroupId(getRandomId());
 		Message message = getMessage(contactGroupId);
-		BdfList body = BdfList.of(1, propsDict);
+		BdfList body = BdfList.of(1, someClientSupports, someServerSupports,
+				propsDict);
 		Metadata meta = new Metadata();
 		BdfDictionary metaDictionary = BdfDictionary.of(
 				new BdfEntry(MSG_KEY_VERSION, 1),
@@ -310,8 +356,8 @@ public class MailboxPropertyManagerImplTest extends BrambleMockTestCase {
 			oneOf(clientHelper).getMessageAsList(txn, message.getId());
 			will(returnValue(body));
 			oneOf(clientHelper).parseAndValidateMailboxPropertiesUpdate(
-					propsDict);
+					someClientSupports, someServerSupports, propsDict);
-			will(returnValue(props));
+			will(returnValue(updateMailbox));
 			oneOf(db).resetUnackedMessagesToSend(txn, contact.getId());
 		}});
 
@@ -328,7 +374,8 @@ public class MailboxPropertyManagerImplTest extends BrambleMockTestCase {
 		Contact contact = getContact();
 		GroupId contactGroupId = new GroupId(getRandomId());
 		Message message = getMessage(contactGroupId);
-		BdfList body = BdfList.of(1, propsDict);
+		BdfList body = BdfList.of(1, someClientSupports, someServerSupports,
+				propsDict);
 		Metadata meta = new Metadata();
 		BdfDictionary metaDictionary = BdfDictionary.of(
 				new BdfEntry(MSG_KEY_VERSION, 2),
@@ -361,8 +408,8 @@ public class MailboxPropertyManagerImplTest extends BrambleMockTestCase {
 			oneOf(clientHelper).getMessageAsList(txn, message.getId());
 			will(returnValue(body));
 			oneOf(clientHelper).parseAndValidateMailboxPropertiesUpdate(
-					propsDict);
+					someClientSupports, someServerSupports, propsDict);
-			will(returnValue(props));
+			will(returnValue(updateMailbox));
 			oneOf(db).resetUnackedMessagesToSend(txn, contact.getId());
 		}});
 
@@ -430,23 +477,24 @@ public class MailboxPropertyManagerImplTest extends BrambleMockTestCase {
 			oneOf(db).getContacts(txn);
 			will(returnValue(contacts));
 			oneOf(crypto).generateUniqueId();
-			will(returnValue(props.getAuthToken()));
+			will(returnValue(updateMailbox.getAuthToken()));
 			oneOf(crypto).generateUniqueId();
-			will(returnValue(props.getInboxId()));
+			will(returnValue(updateMailbox.getInboxId()));
 			oneOf(crypto).generateUniqueId();
-			will(returnValue(props.getOutboxId()));
+			will(returnValue(updateMailbox.getOutboxId()));
 			oneOf(contactGroupFactory).createContactGroup(CLIENT_ID,
 					MAJOR_VERSION, contact);
 			will(returnValue(contactGroup));
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					contactGroup.getId());
 			will(returnValue(messageMetadata));
-			expectStoreMessage(txn, contactGroup.getId(), propsDict, 2, true);
+			expectStoreMessage(txn, contactGroup.getId(), 2, someClientSupports,
+					someServerSupports, propsDict, true);
 			oneOf(db).removeMessage(txn, latestId);
 		}});
 
 		MailboxPropertyManagerImpl t = createInstance();
-		t.mailboxPaired(txn, ownProps.getOnion());
+		t.mailboxPaired(txn, ownProps.getOnion(), someServerSupportsList);
 	}
 
 	@Test
@@ -478,8 +526,8 @@ public class MailboxPropertyManagerImplTest extends BrambleMockTestCase {
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					contactGroup.getId());
 			will(returnValue(messageMetadata));
-			expectStoreMessage(txn, contactGroup.getId(), emptyPropsDict,
+			expectStoreMessage(txn, contactGroup.getId(), 2, someClientSupports,
-					2, true);
+					emptyServerSupports, emptyPropsDict, true);
 			oneOf(db).removeMessage(txn, latestId);
 		}});
 
@@ -498,9 +546,10 @@ public class MailboxPropertyManagerImplTest extends BrambleMockTestCase {
 				new BdfEntry(MSG_KEY_LOCAL, false)
 		);
 		Map<MessageId, BdfDictionary> messageMetadata = new LinkedHashMap<>();
-		MessageId fooUpdateId = new MessageId(getRandomId());
+		MessageId messageId = new MessageId(getRandomId());
-		messageMetadata.put(fooUpdateId, metaDictionary);
+		messageMetadata.put(messageId, metaDictionary);
-		BdfList fooUpdate = BdfList.of(1, propsDict);
+		BdfList body = BdfList.of(1, someClientSupports, someServerSupports,
+				propsDict);
 
 		context.checking(new Expectations() {{
 			oneOf(db).getContact(txn, contact.getId());
@@ -511,17 +560,17 @@ public class MailboxPropertyManagerImplTest extends BrambleMockTestCase {
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					contactGroup.getId());
 			will(returnValue(messageMetadata));
-			oneOf(clientHelper).getMessageAsList(txn, fooUpdateId);
+			oneOf(clientHelper).getMessageAsList(txn, messageId);
-			will(returnValue(fooUpdate));
+			will(returnValue(body));
 			oneOf(clientHelper).parseAndValidateMailboxPropertiesUpdate(
-					propsDict);
+					someClientSupports, someServerSupports, propsDict);
-			will(returnValue(props));
+			will(returnValue(updateMailbox));
 		}});
 
 		MailboxPropertyManagerImpl t = createInstance();
 		MailboxPropertiesUpdate remote =
 				t.getRemoteProperties(txn, contact.getId());
-		assertTrue(mailboxPropertiesUpdateEqual(remote, props));
+		assertTrue(mailboxPropertiesUpdateEqual(remote, updateMailbox));
 	}
 
 	@Test
@@ -549,7 +598,7 @@ public class MailboxPropertyManagerImplTest extends BrambleMockTestCase {
 	}
 
 	@Test
-	public void testGetRemotePropertiesReturnsNullBecauseEmptyUpdate()
+	public void testGetRemotePropertiesNoMailbox()
 			throws Exception {
 		Transaction txn = new Transaction(null, false);
 		Contact contact = getContact();
@@ -559,9 +608,10 @@ public class MailboxPropertyManagerImplTest extends BrambleMockTestCase {
 				new BdfEntry(MSG_KEY_LOCAL, false)
 		);
 		Map<MessageId, BdfDictionary> messageMetadata = new LinkedHashMap<>();
-		MessageId fooUpdateId = new MessageId(getRandomId());
+		MessageId messageId = new MessageId(getRandomId());
-		messageMetadata.put(fooUpdateId, metaDictionary);
+		messageMetadata.put(messageId, metaDictionary);
-		BdfList fooUpdate = BdfList.of(1, emptyPropsDict);
+		BdfList body = BdfList.of(1, someClientSupports, emptyServerSupports,
+				emptyPropsDict);
 
 		context.checking(new Expectations() {{
 			oneOf(db).getContact(txn, contact.getId());
@@ -572,15 +622,17 @@ public class MailboxPropertyManagerImplTest extends BrambleMockTestCase {
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					contactGroup.getId());
 			will(returnValue(messageMetadata));
-			oneOf(clientHelper).getMessageAsList(txn, fooUpdateId);
+			oneOf(clientHelper).getMessageAsList(txn, messageId);
-			will(returnValue(fooUpdate));
+			will(returnValue(body));
 			oneOf(clientHelper).parseAndValidateMailboxPropertiesUpdate(
-					emptyPropsDict);
+					someClientSupports, emptyServerSupports, emptyPropsDict);
-			will(returnValue(null));
+			will(returnValue(updateNoMailbox));
 		}});
 
 		MailboxPropertyManagerImpl t = createInstance();
-		assertNull(t.getRemoteProperties(txn, contact.getId()));
+		MailboxPropertiesUpdate remote =
+				t.getRemoteProperties(txn, contact.getId());
+		assertTrue(mailboxPropertiesUpdateEqual(remote, updateNoMailbox));
 	}
 
 	@Test
@@ -594,9 +646,10 @@ public class MailboxPropertyManagerImplTest extends BrambleMockTestCase {
 				new BdfEntry(MSG_KEY_LOCAL, true)
 		);
 		Map<MessageId, BdfDictionary> messageMetadata = new LinkedHashMap<>();
-		MessageId fooUpdateId = new MessageId(getRandomId());
+		MessageId messageId = new MessageId(getRandomId());
-		messageMetadata.put(fooUpdateId, metaDictionary);
+		messageMetadata.put(messageId, metaDictionary);
-		BdfList fooUpdate = BdfList.of(1, propsDict);
+		BdfList body = BdfList.of(1, someClientSupports, someServerSupports,
+				propsDict);
 
 		context.checking(new Expectations() {{
 			oneOf(db).getContact(txn, contact.getId());
@@ -607,17 +660,17 @@ public class MailboxPropertyManagerImplTest extends BrambleMockTestCase {
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					contactGroup.getId());
 			will(returnValue(messageMetadata));
-			oneOf(clientHelper).getMessageAsList(txn, fooUpdateId);
+			oneOf(clientHelper).getMessageAsList(txn, messageId);
-			will(returnValue(fooUpdate));
+			will(returnValue(body));
 			oneOf(clientHelper).parseAndValidateMailboxPropertiesUpdate(
-					propsDict);
+					someClientSupports, someServerSupports, propsDict);
-			will(returnValue(props));
+			will(returnValue(updateMailbox));
 		}});
 
 		MailboxPropertyManagerImpl t = createInstance();
 		MailboxPropertiesUpdate local =
 				t.getLocalProperties(txn, contact.getId());
-		assertTrue(mailboxPropertiesUpdateEqual(local, props));
+		assertTrue(mailboxPropertiesUpdateEqual(local, updateMailbox));
 	}
 
 	@Test
@@ -645,7 +698,7 @@ public class MailboxPropertyManagerImplTest extends BrambleMockTestCase {
 	}
 
 	@Test
-	public void testGetLocalPropertiesReturnsNullBecauseEmptyUpdate()
+	public void testGetLocalPropertiesNoMailbox()
 			throws Exception {
 		Transaction txn = new Transaction(null, false);
 		Contact contact = getContact();
@@ -655,9 +708,10 @@ public class MailboxPropertyManagerImplTest extends BrambleMockTestCase {
 				new BdfEntry(MSG_KEY_LOCAL, true)
 		);
 		Map<MessageId, BdfDictionary> messageMetadata = new LinkedHashMap<>();
-		MessageId fooUpdateId = new MessageId(getRandomId());
+		MessageId messageId = new MessageId(getRandomId());
-		messageMetadata.put(fooUpdateId, metaDictionary);
+		messageMetadata.put(messageId, metaDictionary);
-		BdfList fooUpdate = BdfList.of(1, emptyPropsDict);
+		BdfList body = BdfList.of(1, someClientSupports, emptyServerSupports,
+				emptyPropsDict);
 
 		context.checking(new Expectations() {{
 			oneOf(db).getContact(txn, contact.getId());
@@ -668,21 +722,25 @@ public class MailboxPropertyManagerImplTest extends BrambleMockTestCase {
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					contactGroup.getId());
 			will(returnValue(messageMetadata));
-			oneOf(clientHelper).getMessageAsList(txn, fooUpdateId);
+			oneOf(clientHelper).getMessageAsList(txn, messageId);
-			will(returnValue(fooUpdate));
+			will(returnValue(body));
 			oneOf(clientHelper).parseAndValidateMailboxPropertiesUpdate(
-					emptyPropsDict);
+					someClientSupports, emptyServerSupports, emptyPropsDict);
-			will(returnValue(null));
+			will(returnValue(updateNoMailbox));
 		}});
 
 		MailboxPropertyManagerImpl t = createInstance();
-		assertNull(t.getLocalProperties(txn, contact.getId()));
+		MailboxPropertiesUpdate local =
+				t.getLocalProperties(txn, contact.getId());
+		assertTrue(mailboxPropertiesUpdateEqual(local, updateNoMailbox));
 	}
 
 	private void expectStoreMessage(Transaction txn, GroupId g,
-			BdfDictionary properties, long version, boolean local)
+			long version, BdfList clientSupports, BdfList serverSupports,
+			BdfDictionary properties, boolean local)
 			throws Exception {
-		BdfList body = BdfList.of(version, properties);
+		BdfList body = BdfList.of(version, clientSupports, serverSupports,
+				properties);
 		Message message = getMessage(g);
 		long timestamp = message.getTimestamp();
 		BdfDictionary meta = BdfDictionary.of(

bramble-core/src/test/java/org/briarproject/bramble/mailbox/MailboxPropertyValidatorTest.java

@@ -9,7 +9,9 @@ import org.briarproject.bramble.api.data.MetadataEncoder;
 import org.briarproject.bramble.api.mailbox.MailboxAuthToken;
 import org.briarproject.bramble.api.mailbox.MailboxFolderId;
 import org.briarproject.bramble.api.mailbox.MailboxPropertiesUpdate;
+import org.briarproject.bramble.api.mailbox.MailboxPropertiesUpdateMailbox;
 import org.briarproject.bramble.api.mailbox.MailboxPropertyManager;
+import org.briarproject.bramble.api.mailbox.MailboxVersion;
 import org.briarproject.bramble.api.sync.Group;
 import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.system.Clock;
@@ -18,7 +20,9 @@ import org.jmock.Expectations;
 import org.junit.Test;
 
 import java.io.IOException;
+import java.util.List;
 
+import static java.util.Collections.singletonList;
 import static org.briarproject.bramble.test.TestUtils.getGroup;
 import static org.briarproject.bramble.test.TestUtils.getMessage;
 import static org.briarproject.bramble.test.TestUtils.getRandomId;
@@ -29,7 +33,12 @@ public class MailboxPropertyValidatorTest extends BrambleMockTestCase {
 	private final ClientHelper clientHelper = context.mock(ClientHelper.class);
 
 	private final BdfDictionary bdfDict;
-	private final MailboxPropertiesUpdate mailboxProps;
+	private final BdfList emptyServerSupports;
+	private final BdfList someClientSupports;
+	private final List<MailboxVersion> someClientSupportsList;
+	private final BdfList someServerSupports;
+	private final MailboxPropertiesUpdateMailbox updateMailbox;
+	private final MailboxPropertiesUpdate updateNoMailbox;
 	private final Group group;
 	private final Message message;
 	private final MailboxPropertyValidator mpv;
@@ -38,11 +47,21 @@ public class MailboxPropertyValidatorTest extends BrambleMockTestCase {
 		// Just dummies, clientHelper is mocked so our test is a bit shallow;
 		//  not testing
 		//  {@link ClientHelper#parseAndValidateMailboxPropertiesUpdate(BdfDictionary)}
+		emptyServerSupports = new BdfList();
+		someClientSupports = BdfList.of(BdfList.of(1, 0));
+		someClientSupportsList = singletonList(new MailboxVersion(1, 0));
+		someServerSupports = BdfList.of(BdfList.of(1, 0));
 		bdfDict = BdfDictionary.of(new BdfEntry("foo", "bar"));
-		mailboxProps = new MailboxPropertiesUpdate("baz",
+
+		updateMailbox = new MailboxPropertiesUpdateMailbox(
+				singletonList(new MailboxVersion(1, 0)),
+				singletonList(new MailboxVersion(1, 0)),
+				"baz",
 				new MailboxAuthToken(getRandomId()),
 				new MailboxFolderId(getRandomId()),
 				new MailboxFolderId(getRandomId()));
+		updateNoMailbox = new MailboxPropertiesUpdate(someClientSupportsList);
+
 
 		group = getGroup(MailboxPropertyManager.CLIENT_ID,
 				MailboxPropertyManager.MAJOR_VERSION);
@@ -56,12 +75,13 @@ public class MailboxPropertyValidatorTest extends BrambleMockTestCase {
 
 	@Test
 	public void testValidateMessageBody() throws IOException {
-		BdfList body = BdfList.of(4, bdfDict);
+		BdfList body =
+				BdfList.of(4, someClientSupports, someServerSupports, bdfDict);
 
 		context.checking(new Expectations() {{
 			oneOf(clientHelper).parseAndValidateMailboxPropertiesUpdate(
-					bdfDict);
+					someClientSupports, someServerSupports, bdfDict);
-			will(returnValue(mailboxProps));
+			will(returnValue(updateMailbox));
 		}});
 
 		BdfDictionary result =
@@ -82,14 +102,15 @@ public class MailboxPropertyValidatorTest extends BrambleMockTestCase {
 	}
 
 	@Test
-	public void testEmptyPropertiesReturnsNull() throws IOException {
+	public void testEmptyProperties() throws IOException {
 		BdfDictionary emptyBdfDict = new BdfDictionary();
-		BdfList body = BdfList.of(42, emptyBdfDict);
+		BdfList body = BdfList.of(42, someClientSupports, emptyServerSupports,
+				emptyBdfDict);
 
 		context.checking(new Expectations() {{
 			oneOf(clientHelper).parseAndValidateMailboxPropertiesUpdate(
-					emptyBdfDict);
+					someClientSupports, emptyServerSupports, emptyBdfDict);
-			will(returnValue(null));
+			will(returnValue(updateNoMailbox));
 		}});
 
 		BdfDictionary result =