Index: channels/chan_sip.c
diff -Nau channels/chan_sip.c.orig channels/chan_sip.c
--- channels/chan_sip.c.orig	2011-01-14 18:32:52.000000000 +0100
+++ channels/chan_sip.c	2011-03-13 14:34:29.000000000 +0100
@@ -24267,6 +24267,7 @@
 	/* Called with peerl lock, but releases it */
 	struct sip_pvt *p;
 	int newmsgs = 0, oldmsgs = 0;
+	char *s = NULL;
 
 	if (ast_test_flag((&peer->flags[1]), SIP_PAGE2_SUBSCRIBEMWIONLY) && !peer->mwipvt)
 		return 0;
@@ -24307,6 +24308,11 @@
 		}
 		/* Recalculate our side, and recalculate Call ID */
 		ast_sip_ouraddrfor(&p->sa, &p->ourip, p);
+		/* Set the username = mailbox and remove the context */
+		ast_string_field_build(p, username, "%s", peer->name);
+		s = strchr(p->username, '@');
+		if (s != NULL)
+			*s = 0;
 		build_via(p);
 		ao2_t_unlink(dialogs, p, "About to change the callid -- remove the old name");
 		build_callid_pvt(p);