This is in response to my previous question "Sending notification.ind to multiple clients".
You've mentioned that the message-id is unique for every mms notification. Do you mean transaction-id? I've checked the WAP-209 and the only id being mentioned on the notification.ind is transaction-id.
Another question, exactly who is the one refusing the retrieval of the mms when the transaction-id is not unique? Is it the phone or the proxy rejecting the retrieval command?