I am having a problem that was posted here as well and I've looked through and couldn't find the answer. The problem is that emails with attachments are bouncing back, regardless to which domain are sent. Error is:
This message is larger than the current system limit or the recipient's mailbox is full. Create a shorter message body or remove attachments and try sending it again.
<server.EDI.local #5.2.3 smtp;450 5.2.3 Msg Size greater than allowed by Remote Host>
I've seen lots of "the problem is on recipients end" but its not (I know what the message says :-))... I've gone through the Exchange and increased limits on Mailboxes, SMTP connector (although none is used), policy (none used) public folder and individual mailboxes. We do use ASSP and went through that as well and no blocking of attachments (externally or internally) is applied. I am hitting a wall here and the client is getting ticked off. Any help, hint would be greately appreciate it.