Wireshark-users: [Wireshark-users] Bizarre mail issue on network, Please someone, help.
From: "S R" <[email protected]>
Date: Wed, 18 Apr 2007 23:18:15 -0400

I was wondering if someone would be so kind as to help me in figuring out a strange mail problem I'm having.  I'm having a ton of retransmissions with mail, and it's sitting it the queue on my relay server.  I thought at first it was some problem with my firewalls, but I'm starting to think that's not the case.  I've run a capture on my relay server, and I'm starting to think it may be something with my switch/router.... something in between - and perhaps these messages aren't even making it to the firewall.

I'm having some problems interpreting this log, but it appears at times that I'm not getting an ACK from my router, so I retransmit, which continues for 2 days until the timeout and the msg bounces with a rejection notice.

However, it's even more bizarre because I haven't located any packet loss.  I don't think it's an MTU problem, and the only time I can replicate the email issue is by attempting to send .html attachments (not embedded)  They aren't being received inbound and not reaching the recipient outbound.

This is a major issue, as it's backing up my queues, and we have some applications that mail html attachments for reporting, etc.

Can anyone help me? I have dissected about everything I can think of.  There are no rules on my Firewalls to prevent any attachments, no filtering is turned on with my mail server or firewall.

TIA!!  I hope you all can find it in your heart to help me retain my sanity.