diff --git a/Mailbox-Properties-Client.md b/Mailbox-Properties-Client.md
index a152562..c5c440c 100644
--- a/Mailbox-Properties-Client.md
+++ b/Mailbox-Properties-Client.md
@@ -1,9 +1,9 @@
 
-The mailbox properties client is a [BSP client](https://code.briarproject.org/briar/briar-spec/blob/master/protocols/BSP.md) that synchronises mailbox properties between pairs of devices. Mailbox properties describe how to connect to a mailbox associated with a device.
+The mailbox properties (or updates) client is a [BSP client](https://code.briarproject.org/briar/briar-spec/blob/master/protocols/BSP.md) that synchronises mailbox properties and supported mailbox api versions between pairs of devices. The properties describe how to connect to a mailbox associated with a device.
 
 ### Identifier
 
-The client's identifier is `org.briarproject.bramble.mailbox`. The major version is 1.
+The client's identifier is `org.briarproject.bramble.mailbox.properties`. The major version is 1.
 
 ### Groups
 
@@ -13,11 +13,11 @@ The client uses a separate BSP group for communicating with each contact. The [g
 
 **UPDATE** - The message body is a BDF list with 4 elements: `version` (int), `clientSupports` (list), and `serverSupports` (list), `properties` (dictionary).
 
-`version` is incremented whenever the properties change.
+`version` is incremented with each new update message.
 
-`clientSupports` is a non-empty list of Mailbox API versions that the sender can talk to as a client. Each element (a version) is a list with 2 elements: `major` (int), `minor` (int).
+`clientSupports` is a non-empty list of Mailbox API versions that the sender's Briar instance can talk to as a client. Each element (a version) is a list with 2 elements: `major` (int), `minor` (int).
 
-`serverSupports` is a list of Mailbox API versions that the sender's mailbox supports. The list must be empty if `properties` is empty (there is no mailbox), otherwise it must be non-empty. Each element (a version) is a list with 2 elements: `maj` (int), `min` (int).
+`serverSupports` is a list of Mailbox API versions that the sender's Mailbox supports. The list must be empty if `properties` is empty (there is no mailbox), otherwise it must be non-empty. Each element (a version) is a list with 2 elements: `maj` (int), `min` (int).
 
 The keys of the `properties` dictionary are strings. The dictionary of a well-formed update contains either no (0) entries, which means for the receiver that there is no mailbox available. Or, it contains all of the following entries: