I have an SBS 2008 client installation where the Exchange Server has stopped receiving inbound mail. When I send email to the server from my office, I first get a message that the email was delayed. Then after several hours, I get a non-delivery report stating "#550 4.4.7 QUEUE.Expired; message expired ##"
I can telnet to the server and send a message.When I send it, it says "added to queue".
I can send mail outbound just fine. The issue is only with inbound mail.
I ran the mail flow troubleshooter and it failed with a message "Mail submission failed: Error message: Server does not support secure connections.."
This led me to believe that the problem was the certificate. I believe that the server was installed with a self-signed certificate but it is less than a year old so I do not think that is is because the certificate has expired.