Morten Stevens mstevens@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@gmail.com