You can't prefix this one with MWI as it ends up in the body of the MWI notify…

You can't prefix this one with MWI as it ends up in the body of the MWI notify causing some devices to have a heart attack

src/mod/applications/mod_voicemail/mod_voicemail.c

@@ -1918,7 +1918,7 @@ static void update_mwi(vm_profile_t *profile, const char *id, const char *domain
 		yn = "yes";
 	}
 	switch_event_add_header_string(event, SWITCH_STACK_BOTTOM, "MWI-Messages-Waiting", yn);
-	switch_event_add_header_string(event, SWITCH_STACK_BOTTOM, "MWI-Update-Reason", update_reason);
+	switch_event_add_header_string(event, SWITCH_STACK_BOTTOM, "Update-Reason", update_reason);
 	switch_event_add_header(event, SWITCH_STACK_BOTTOM, "MWI-Message-Account", "%s@%s", id, domain_name);
 	/* 
 	switch_event_add_header(event, SWITCH_STACK_BOTTOM, "MWI-Voice-Message", "%d/%d (%d/%d)", total_new_messages, total_saved_messages,