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Re: [suse-security] Postfix Backscatter

my postfix-Mailserver on a SuSE9.1 system ist flooded by backscatter
mails which are undeliverable (random addresses).

At the moment it is nearly impossible to sent a mail to this system.
Yesterday it handled (rejected) about 12.000 of such mails.

This seems to be too slow.

So i changed my configuration setting:
smtpd_error_sleep_time = 0,
stopped all RBL usage
increased the number of smtp processes from 2 to 80.

Now my system seems to handle about 40.000/day but this is not enough,
there is still only a small chance to send a normal mail.

Is there any chance to optimize postfix so that it can handle much more
mails/connections each day?
Or any other idea to solve such backscatter problems?


You want to reduce the time Postfix holds mail and tries to deliver it. The default is 5 days which means X messages stuck in the queue will be bouncing around for 5 days,with Postfix attempting delivery every 1000 seconds (16 minutes or so), causing a ton of attempted deliveries. In you main.cf you want to set:

maximal_queue_lifetime = 5d

to something shorter, like maybe 1 day, or a few hours only. You might also want to increase the queue_run_delay

queue_run_delay = 1000s

Which will reduce the number of attempts to deliver it. This is all covered in sample-rate.cf.

Kurt Seifried, kurt@xxxxxxxxxxxx
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