On Wed, Apr 16, 2014 at 02:17:23PM -0500, Brian Grimal wrote:
> 14:04:31.425682 IP 172.16.5.8.25 > 206.46.173.11.19129: Flags [P.], seq
> 35:216, ack 32, win 46, options [nop,nop,TS val 386720906 ecr 1770681376],
> length 181
> ..&.&mO....-..........J.
> ....i.t 250-mail.AAAAA.com
> 250-PIPELINING
> 250-SIZE 30720000
> 250-VRFY
> 250-ETRN
> 250-STARTTLS
> 250-AUTH LOGIN PLAIN
> 250-AUTH=LOGIN PLAIN
> 250-ENHANCEDSTATUSCODES
> 250-8BITMIME
> 250 DSN
>
> 14:04:31.445742 IP 206.46.173.11.19129 > 172.16.5.8.25: Flags [.], ack 216,
> win 33304, options [nop,nop,TS val 1770681378 ecr 386720906], length 0
> ........ ...........J....&mO
> i.t"....
The remote system ACKs the EHLO reply. After 10 seconds of silence
from the remote system (see Wietse's reply about stress-dependent
timeouts) your Postfix replies with a 421 timeout:
> 14:04:41.434870 IP 172.16.5.8.25 > 206.46.173.11.19129: Flags [P.], seq
> 216:266, ack 32, win 46, options [nop,nop,TS val 386721907 ecr 1770681378],
> length 50
> ....&mO....,..........J.
> ...si.t"421 4.4.2 mail.AAAAA.com Error: timeout exceeded
But the remote system is no longer reachable, and this reply is
re-transmitted multiple times!
> 14:04:41.434892 IP 172.16.5.8.25 > 206.46.173.11.19129: Flags [F.], seq 266,
> ack 32, win 46, options [nop,nop,TS val 386721907 ecr 1770681378], length 0
> .&mO....F.............J.
> ...si.t"
> 14:04:41.648557 IP 172.16.5.8.25 > 206.46.173.11.19129: Flags [P.], seq
> 216:266, ack 32, win 46, options [nop,nop,TS val 386721929 ecr 1770681378],
> length 50
> ....&mO....,..........J.
> ....i.t"421 4.4.2 mail.AAAAA.com Error: timeout exceeded
>
> 14:04:42.088568 IP 172.16.5.8.25 > 206.46.173.11.19129: Flags [P.], seq
> 216:266, ack 32, win 46, options [nop,nop,TS val 386721973 ecr 1770681378],
> length 50
> ....&mO....,..........J.
> ....i.t"421 4.4.2 mail.AAAAA.com Error: timeout exceeded
Some firewall or load-balancer or similar device is losing connection
state on the network path between your server and the SMTP clients.
You'll have to track down the culprit.
--
Viktor.
