I manage an Exchange 2003 email server for a customer that has recently started having problems receiving from certain domains.
I've been watching the logs and found that the typical SMTP "conversation" for the problem domains doesn't include any DATA commands. You can see a small excerpt of the log in the attached file.
All the domains that have trouble send to my customer do the EHLO, MAIL, and RCPT commands, then wait several minutes and then QUIT. Some of the domains show QUIT in just a few minutes, while others wait until the connection times out and then quit.
DNS appear to be correct (reverse also) and the Exchange 03 is up to date. The customer is on DSL and although the connection is busy, it's certainly not overloaded. This happens consistently for certain domains - their email never gets through while other flow right through every time.
I really need to fix this!