This server has been working for a few months now but we just started noticing this issue. I am getting only certain emails stuck in the exchange 2003 queue. When I click on the emails in the bottom left in the exchange system manager it says "An SMTP protocol error ocurred." Some of the emails are returned back to the user and have the following error: Relay access denied (in reply to RCPT TO command)
Here is a report from mxtoolbox, which shows " Warning - Reverse DNS does not match SMTP Banner". I am thinking this is somehow related to the other issues, am I correct?
220 cs.server.local Microsoft ESMTP MAIL Service, Version: 6.0.3790.3959 ready at Thu, 25 Mar 2010 11:34:44 -0400
Not an open relay.
0 seconds - Good on Connection time
0.078 seconds - Good on Transaction time
OK - 18.104.22.168 resolves to
Warning - Reverse DNS does not match SMTP Banner
250 cs.server.local Hello [22.214.171.124] [47 ms]
MAIL FROM: <email@example.com>
454 5.7.3 Client does not have permission to submit mail to this server. [31 ms]