Have a situation with a client right now where the mail queue is stacking up on a sbs 2003 r2 server. when viewing the queue i can see the following error:
The connection was dropped due to an SMTP protocol event sink.
Ive tried restarting the exchange server and firewall. I can receive email no problem but am unable to send. DNS appears to be working correctly and a DNS report does not spit back any red flags.