Iphone

Hello. For one of my users I have set Exchange to forward a copy of all incoming emails to her Blackberry push email account at instantemail.t-mobile.co.uk.
As all regular outbound emails go through a smart relay (SMTP mail relay server - authenticated SMTP service, mobile / relaying denied and SMTP errors solved.) these forwarded emails get routed via DNS through their own connector.
This has all worked well for some time.

For no apparent reason today messages kept building up in their queue. When the queue in question is highlighted, a message appears below ...

"An SMTP protocol error has occured"

New messages arrive in the queue all the time (as copies of new messages rec'd).

Have tried;

1. Force connection
2. Restart SMTP service
3. Pause the service for a while
3. Restart SBS2003 server

... all to no avail.

How can I zap these messages and 'flush' or clear the queue?

This did happen once before (for this particular routing / queue) but a few hours later it all cleared. Hasn't done so this time and my user is getting withdrawal symptoms on her blackberry!

The only thing I did differenly today wa I was testing out an Astaro Security Gateway for an hour on the live system early in the morning. But no changes were made to the server at all.
I've checked that the SBS2003 machine can 'ping' the tmobile server (it can).