We have a strange situation that I am trying to resolve.
One of our users is reporting that some emails that contain attachments are not coming through to them. After some investigation it appears that they do infact recieve the emails but the attachment is missing.
I check the message tracking logs and what appears to be happening is that the server recieves an email, which is then forwarded to the correct mailbox. A couple of minutes later another email, from the same sender is recieved - but this is much larger so I'm assuming contains the attachment. This email has the same messageId as the previous email and as a result appears not to be delivered to the users mailbox, instead being marked with an EventID of DUPLICATEDELIVER.
Can anyone shed any light on the situation?
Looks like this is related to antivirus or antispam software.
http://forums.msexchange.org/m_1800460467/mpage_1/key_/tm.htm#1800460467
I'm looking at this as well and actually have come to the conclusion it is due to the paging/resource usage of exchange. Our server has only 6GB ram and sqlserver.exe is using 1GB at all times, resource monitor shows 20-50MB/s disk usage by it as well.
We will do a reboot and see what happens otherwise will look at upgrading the ram. I've read somewhere that this can happen with exchange when it is running out of resources, but I can't remember from where.