i'm currently running exchange 2010. lately, some emails sent to some of our email boxes are not getting delivered. for example, an outside sender writes an email to user1, user2, user3. user1 and user3 will receive the email but user2 never gets it. there are no failures in message tracking. if that outside sender tries to send an email to JUST user2, message tracking doesn't acknowledge the existence of that email at all. it just doesn't show up. this happens to a few specific email boxes on our server and seems to happen with specific senders too.

how do i start to track down the problem?

  • i checked smtp protocol logs, the message doesn't show up there either. what's one step before that? – Elizabeth Greenwood Nov 8 '12 at 1:47
  • the "first" step is technically to check on the sending side. Check to make sure it gets "out" and sent to your mail server. Test with other senders like a gmail account. You need to look at the entire message flow from sender to receiver ideally, not in reverse. – TheCleaner Nov 9 '12 at 16:49

If message tracking for user2 nevers shows up with a test email, even from say gmail, then check for undeliverables back to gmail first (or whatever the test sender is).

Try an SMTP test (various online tools or just telnet: http://support.microsoft.com/kb/153119)

Verify that outbound email from user2 works, and check the headers on the remote receiver side to ensure it looks right too (for instance, FROM address is correct)

Finally, if there are layers in the middle, such as an email gateway, SaaS, virus/spam software, etc. you should check those as well.


You should start with the SMTP protocol logs on the server(s) where incoming messages are delivered; if you are using Edge servers, start there and check whether they actually got the messages at all. If you are receiving Internet email directly on Hub Transport servers, do the same there. If you are using any other spam/virus filtering solution before the messages get to any Exchange server, have a look there, too.

You should examine every step in the delivery chain starting from the server(s) where the MX record(s) for your SMTP domain is/are pointing, and find where the messages are being discarded.

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