We have been receiving complaints about random missing emails. A user knows an email has been sent to them, and has received other emails from the sender (even perhaps a few minutes earlier), but some emails (mostly with attachments?) never arrive.
I check our spam filter and find nothing. There is also no record of the missing emails in the Message Tracking on our Exchange 2007 server, or in the Exchange queues.
If I put the sender's domain in our Positni spam white list, it doesn't seem to help. The sender also never gets a rejection or a return on the email they send.
Is there a possibility our server is "receiving" the emails but never processing them?
I'm at a loss in trying to figure out what is happening.