Re: [Exim] Exchange, HELO and underscores

>From: "Richard.Hall" <richard.hall@???>
>To: exim-users@???
>Subject: [Exim] Exchange, HELO and underscores
>Sender: exim-users-admin@???
>Date: Thu, 26 Jun 2003 17:49:34 +0100 (BST)
>
>Yes, I know it's an old chestnut, but I still have to fight this
>battle occasionally. This time the opposition is resisting, and I
>need chapter and verse, moral support, advice, and anything else
>that's going.
>
>I'm running Exim 4.12 on Solaris 8. A misconfigured Exchange server
>is sending me a HELO name with an underscore in it.

...

>b) swear blind that nothing has changed (except that I now reject
>them later than I used to) - but why do they claim it has changed
>recently - or was it different on Exim 3, which one of my other
>MX's was running?

The default on exim3 was more lax. You needed to set the main
configuration option:

helo_strict_syntax = true

in the main configuration section to get this behaviour. The
default for helo_strict_syntax was false and so HELO/EHLO names
containing underscores would be accepted.

>c) tell them that lots of other people would reject their mail - is
>that true?

Not here. I gave up on this when I saw quite a few incoming
connections containing these HELO/EHLO names. So my exim4
configuration file contains:

# exim4 enforces strict syntax checking on the HELO or EHLO message.
# However I suppose we'd better allow the underscore character.
# Some sad scrotes running mail services on NT boxes think they can
# include this character in the greeting message.
helo_allow_chars = _