diff --git a/Mailbox-Properties-Client.md b/Mailbox-Properties-Client.md
index 2702550..3a761c6 100644
--- a/Mailbox-Properties-Client.md
+++ b/Mailbox-Properties-Client.md
@@ -11,7 +11,7 @@ The client uses a separate BSP group for communicating with each contact. The [g
 
 ### Message types
 
-**UPDATE** - The message body is a BDF list with 4 elements: `version` (int), `properties` (dictionary), `briarSupports` (list), and `mailboxSupports` (list).
+**UPDATE** - The message body is a BDF list with 4 elements: `version` (int), `properties` (dictionary), `clientSupports` (list), and `serverSupports` (list).
 
 `version` is incremented whenever the properties change. The keys of the `properties` dictionary are strings.
 
@@ -22,9 +22,9 @@ For major version 0, the `properties` dictionary of a well-formed update contain
 * "inboxId" : byte[32] -- folder id used when receiving data from the mailbox
 * "outboxId" : byte[32] -- folder id used when delivering data to the mailbox
 
-`briarSupports` is a list of Mailbox versions that this Briar instance supports (can communicate with). It must not be empty. Each element is a list with 2 elements: `maj` (int), `min` (int).
+`clientSupports` is a list of Mailbox API versions that the sender can talk to as a client. It must not be empty. Each element is a list with 2 elements: `maj` (int), `min` (int).
 
-`mailboxSupports` is a list of Briar versions that the mailbox supports. It must be empty if `properties` is empty (there is no mailbox). Each element is a list with 2 elements: `maj` (int), `min` (int).
+`serverSupports` is a list of Mailbox API versions that the sender's mailbox supports. It must be empty if `properties` is empty (there is no mailbox). Each element is a list with 2 elements: `maj` (int), `min` (int).
 
 ### Validity policy