I have a problem with e-mails containing more than 20M of attachments getting stuck in the deferred queue. They will bounce from active to deferred back to active until about 5 or 7 days go by an they will be dropped completely. My web mail MTA timeout is 600 seconds and in our current global settings, our maximum message size is 819200kb (100MB) yet some of the e-mails that are larger than, say, 20M are still getting deferred. Not sure why.