post...@nisny.com:
> There were several attempts from postfix to connect to 6 different mx
> servers to deliver one email. They all have the same result so I'm only
> including the dump of the first here:
We see SYN, SYN|ACK, ACK, and a bunch of retransmissions.
SYN: Initial client window 1400 (scale 6), options [mss 1460,nop,wscale
6,sackOK,TS]
SYN|ACK: Initial server window 33304 (scale 1), options [nop,nop,TS,mss
1460,nop,wscale 1,nop,nop,sackOK].
Then we see SYN|ACK retransmitted, ACK retransmitted, etc., until
the server sends a RESET. The TCP handshake never completes. And
someone may already have posted the solution.
For the telnet connection we have a successful handhake.
SYN: Initial client window 65535 (scale 6), same TCP options as
SMTP client. SYN|ACK: Same initial server window and TCP options
as STMP server.
The only difference I see is the initial 1400 client TCP window
size.
As someone already suggested in one of the first follow-ups:
"Would you mind trying to remove "tcp_windowsize = 1400" from
you configuration (do not forget to issue a "postfix reload"
afterwards!)?"
Wietse
