[Dovecot] what best for anti-spam filter?

[Joseph Tam]

Morten Stevens <mstevens at imt-systems.com> writes:

> So it is now RFC compliant. Anyway I think delaying mail traffic is not
> a good solution.

Well, OK, if you not keen on greylisting, you can try greet pausing,
which introduces a shorter delay.

It tests a bot's patience by inserting a pre-HELO pause.  RFC allows 5
minutes before timeout.  This is last week's stat for one of my mail
server and the count of early-talker or early-disconnecter, almost
all of which are bots.  A greet pause of over 20s dumps a lot of bots.
Expect to whitelist the odd server here and there because they've tuned
their servers to some aggressively small RFC non-compliant timeouts.

 	Delay						Disconnect/early-talkers

 	00                                               =     9
 	01                                               =     1
 	02                                               =     1
 	03                                               =    11
 	04                                               =    34
 	05                                               =     5
 	06                                               =     1
 	07                                               =     1
 	08                                               =     3
 	09                                               =     3
 	10                                               =     9
 	11                                               =     1
 	12                                               =     2
 	16                                               =     7
 	17                                               =    10
 	18                                               =     4
 	19                                               =    17
 	20                                               =  1161
 	21                                               =   431
 	22                                               =    61
 	23                                               =    43
 	24                                               =    13

Joseph Tam <jtam.home at gmail.com>