is it important to say this disconnect seems to happen before mail
transmission, yes, probably after "250 OK"
Correction, in this case, some time later because it is showing some
info about the message
I'm getting lots of these in exim log:
2021-02-25 04:31:15.790 [19189] SSL_write: (from
mail-pu1apc01hn2214.outbound.protection.outlook.com (APC01-PU1-
obe.outbound.protection.outlook.com) [52.100.183.214]:42879)
syscall:
Connection reset by peer
I found this situation because single user forwarded microsoft bounce
message to their user said:
Generating server: AM6PR05MB6309.eurprd05.prod.outlook.com
Total retry attempts: 26
u...@exampl.com
Remote Server returned '550 5.4.300 Message expired -> 451 Temporary
local problem - please try later'
So checking my log I found the last attempt to deliver this message
resulted in this situation where outlook.com immediately dissconnected
(its how I learned about this "connection reset").
The question is: did your exim log a message acceptance (a "<=" line) ?
If so, this 451 is definitively their problem. On the other hand, if
your
system had logged several "Temporary reject" lines referencing this
user
and outlook, it is your problem (and separate from the TCP RST issue).
Does not log either one. In one case, the transation ended with "SMTP
command timeout on TLS connection", on the next attempt, transaction
ended with "SSL_write: ... syscall: Broken pipe"
So I guess outlook.com server is disconnection because it is impatient
or something? I make a mistake that this problem was not "Connection
reset by peer" (only that I noticed those log message when investigating
this situation). I see other "broken pipe" errors from outlook.com but
not nearly as many.
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