What events appear in your application event log related to the SMTP and MTA
I encountered a similar problem which occurred as someone uninstalled and
reinstalled the IIS SMTP service which replaced the Exchange SMTP version.
You can check the SMTP version by telnetting to the your exchange server on
port 25, eg. "telnet EXCHSRVR 25" - this will result in the Exchange server
standard welcome screen, eg.
220 <servername> Microsoft ESMTP Mail Service, Version: 6.0.3790.0 ready at
Fri, 3 Sep 2004 12:10:06 +100
Then type EHLO and check the response received from the Exchange server -
check within the list of ESMPT commands supported for the X-LINK2STATE and
the XECH50 commands. If thery dont appear then you have the standard version
of SMTP and not the Exchange version. To reinstate the Exchange version,
reinstall Exchange from the CD with the "reinstall" option.