We have had some instances were a user A sends user B an email, both are internal exchange accounts. User B does not get the email. User B rants and raves and calls user A who sends the email again and user B now gets it.
I have done the following to try and discover the intermittent problem.
Checked user A sent items and outbox, the email is NOT in the outbox, and both copies, the original and the resent email are in the sent items.
Checked user B inbox, Junk and Deleted folders. Nothing for the first try, yet the second attempt landed in the Inbox as expected.
Checked the message for Spam triggers, nothing
Checked the Anti-Spam and Anti-Virus logs, nothing
I tried to track the messages from User A to User B by using the message tracker in Exchange, message 1 does not show up at all, message 2 does all the expected steps. leaves User A gets to User b.
Checked the firewill logs to see if something there blocked it the first time, nothing.
I'm wondering if anyone has experienced this and how to prevent it from happening again. Are there any tools out there that can help us determine what is going on?