Reminds me of the old “five hundred mile email” https://web.mit.edu/jemorris/humor/500-miles
--srs ________________________________ From: mailop <mailop-boun...@mailop.org> on behalf of Mark Delany via mailop <mailop@mailop.org> Sent: Wednesday, February 19, 2025 4:29:09 AM To: mailop@mailop.org <mailop@mailop.org> Subject: Re: [mailop] SMTP Submission issues with latest macOS Mail.app On 19Feb25, Viktor Dukhovni via mailop apparently wrote: > > Is this regardless of the type of attachment sent? I just tested a > > message with an attached ".txt" file, and it got through submission into > > Postfix just fine. Turns out that small attachments work, but... > You could try Apple's "Connection Doctor" and enable logging of the Good tip. That shows the client sending the full SMTP transaction but only the first 'n' bytes are making it to the server which in turned led us to take a closer look at the network traffic and... ...it turns out to be an asymmetric routing issue. We'd recently added an additional route to the submission server and an unintended side-effect is that the output part of the submission traffic is now sent out one interface and the input part is coming in on another interface - for an infrequently used client subnet. As to why this is causing a problem, I don't yet know, but clearly one of the stacks doesn't like it, or maybe a firewall state is dropping packets. In any event there is now a root cause to work on which is not mail related. Thanks for the suggestions, Viktor. A reminder of that old advice, always be suspicious of recent changes, regardless of how innocent or irrelevant they may seem. Mark. _______________________________________________ mailop mailing list mailop@mailop.org https://list.mailop.org/listinfo/mailop
_______________________________________________ mailop mailing list mailop@mailop.org https://list.mailop.org/listinfo/mailop
