After we updated a new security certificate on our Exchange 2003 server our users have been unable to send messages to people they had already been sending to. Any ideas on why this is happening?
They are getting these messages:
Subject: Undeliverable: subject
Delivery has failed to these recipients or distribution lists:
email@example.com An error occurred while trying to deliver this message to the recipient's e-mail address. Microsoft Exchange will not try to redeliver this message for you. Please try resending this message, or provide the following diagnostic text to your system administrator.
The following organization rejected your message: yyy.com.
EDIT - SOLUTION
It was a setting on our send connector in exchange. It wasn't changed when the new SSL certificate was added. The reverse DNS lookups on our email weren't matching the old setting