Hello Matt,
From the topic of the thread and also the details you've provided, it looks like there may be some network interruptions happening of some being noticed to the domains.
5.4.7 - Delivery expired (message too old) [Default] '[Errno 54] Connection reset by peer' (delivery attempts: 75) would generally mean the connection had seen a RST packet on the transmission thus closing the connection and hard bounce due to the bounce profile with too many reattempts/time in queue.
May i ask if you can attach a copy of the message tracking if possible, also:
I would like to suggest the following commands for initial troubleshooting (all in CLI)
CLI > tophosts
Check the hosts with the '*' next to it.
Follow it up with CLI > hoststatus > <Name of affected host>
It will then show you the last known failure on connections and the routes your ESA will send to.
I would like you to then attempt a telnet to this IP on port 25 and let us know the results.
if the issue is intermittently happening, the best course of action would be to enable a packet capture on your ESA on port 25 (GUI > Help and Support > Packet Capture)
On the CLI : Use the 'delivernow' command to force attempts of delivery then tail mail_logs so you can monitor live traffic, if failures occur again, stop this packet capture and open it on wireshark, you should see the attempts and errors or RST if it comes up; should it be coming from destination side or so, check the MAC address to see the next hop and investigate this next hop for any packet drops or inspections.
Key point:
Ensure no SMTP packet inspections are being done.
Please let us know,
Regards, Matthew
