i have a few emails being delayed from an external sender (only that i know of but could be others).
it hits my mail MTA at 9:02.
immediately i see a return message in the MTA logs from my load balncer VIP IP sayin DSN 4.0.0. message deffered
at 9:21 is see the message queued message in my MTA logs
on the exchange 2013 server, message tracking logs show the message was received at 9:21 and then delivered. i dont see any mails with defer status or any other eventIDs for the delivery of the mails apart form standard ones.
any ideas on where i can look. most external domains can deliver with no delays. this message did have a attachment., but i presume the AV scanning in 2013 is done in the transport pipe line so a delay would should up in message tracking.