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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
and
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?

Best
Uwe

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
A15B BEE5 B391 B9AD B0EF
AEB0 AD63 0B4E AD56 E574
http://seifried.org/security/




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