Hi Viktor, Am 10.09.2014 um 16:19 schrieb Viktor Dukhovni: > Have you tried disabling TCP window scaling? It might be confusing > some middle-box (firewall, NAT device, ...) on path between the > remote systems and your MTA. I would not have thought of that... I've tried that now, but it does not seem to help. > Post the hostname/IP address of the receving system. mail.tuxroot.de > Capture and examine a tcpdump recording of mail from one of the > problem senders. Any sign of retransmission by the sender? I'm trying to get a good dump and will post results once I get one. Not that easy since the external hosts keep changing all the time. All mail affected comes from mass mailers that use server clusters, so I keep getting those messages from lots of different remote hosts. I'm waiting for it to happen from one of the hosts I've seen before.
Retransmission is tried numerous times, but for every retransmission the lost connection message is the same (identical number of bytes), as far as I can tell. That's one thing that puzzles me... So e.g. a message is delivered twice and each time the connection is lost after exactly 17441 bytes, even if it's different remote hosts trying, that's kind of odd. > For at least one such session, post all related messages from the > "postfix/smtpd[pid]" that occur between "connect from" and > "disconnect from". Here's one: http://pastebin.com/twb3Z8Eg And this seems to be the same message being redelivered later, from a different host, with the same result (connection lost after exactly 17441 bytes): http://pastebin.com/Qihbjz3w What I do notice there is that in fact the connection seems to be *very* slow. In the above example, the whole process takes several minutes. I don't have any throughput or network speed issues with other hosts, though. I've tried sending mail from Gmail, Yahoo, my workplace, my former university, GMX, whatever; everything goes through on the first attempt each and every time, and quickly. But it seems it is always slow for a few hosts. Regards, Sean
