Ioannis Tsouvalas:
> >
> >Ioannis Tsouvalas:
> >> 451 Requested action aborted: local error in processing
> >> 451 Temporary local problem - please try later
These you can do nothing about, except perhaps retry when the remote
system is under less stress.
> >> 421 4.4.1 Connection timed out (in reply to end of DATA command)
> >> 421 4.4.2 mxfront39.mail.yandex.net Error: timeout exceeded (in
> >> reply to end of DATA command)
These could be a network-level problem such as broken IP path MTU
discovery, or TCP options that are mis-implemented by an and system
or by an intermediate system (such as a cheap firewall).
There is some 12 years of discussion archived on-line that covers
IP path MTU problems, and some 5 years for mis-implemented TCP
options (Sack, Wscale, ...). I see that you have already turned
off some of those.
This can be debugged by capturing network packets and making sense
of the flags, windows, ACK offsets, and retransmissions. I have
done that in earlier years but can no longer afford the time.
Wietse
