Re: Filtering HELO / EHLO names before MAIL FROM

On 2025-01-03 20:07, Grant Taylor wrote:

Hi,
 Is there a method that I can use to filter & reject (return a 5xy error) for bad HELO / EHLO names at HELO / EHLO time?
 I see some options (FEATURE(`block_bad_helo')) but they seem to apply later in the SMTP transaction.
 I'm seeing what I suspect is bots looking to do credential stuffing, but I'm not offering authentication on this system, so they are bailing before usual protections would kick in.
 Initial searches haven't turned up much that happens before MAIL FROM.

`milter-cli` could do it using an `envelope-from=` filter.  Failing that I suppose I could tweak one of my other milters.
BarricadeMX has the ability (not a milter).
--
Anthony C Howe
achowe@snert.com                                   BarricadeMX & Milters
http://nanozen.snert.com/                          http://software.snert.com/