> On Aug 29, 2018, at 1:53 PM, Fazzina, Angelo <angelo.fazz...@uconn.edu> wrote:
>
> [root@mail4 log]# cat maillog-20180829 |grep 137.99.149.148 |grep -v
> disconnect |grep -v submission|grep connect
You forgot to aggregate:
$ ... | awk '{print $3}' | sed -e 's/.:..$/0/' | uniq -c
15 09:20
28 09:30
30 09:40
20 09:50
28 10:00
33 10:10
10 10:20
So that's a peak rate of of 33 messages per 10 minutes, or 3
messages a minute! With mail transactions lasting just a couple
of seconds, and average connection spacing at ~20 seconds,
the client is spending most of its time disconnected or waiting
for the SMTP banner.
One possibility is that you don't have enough smtpd(8) process
concurrency. If your server is busy handling lots of concurrent
traffic, perhaps it reaches the $default_process_limit often, and
the client's connection are stuck waiting for a free process to
accept a new connection.
You should try connecting to the relevant port on your server
a few times (spaced minutes apart) and see how long you typically
need to wait before you see a 220 banner? (The same port the
user is using to submit mail, not clear whether it is 25 or 587).
The default process limits in Postfix date back to Y2K hardware,
and servers have a lot more RAM, CPU and network bandwidth these
days.
--
Viktor.
