Morten Stevens <mstev...@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.h...@gmail.com>

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