Re: [exim] server with underscored Helo

Leonardo Boselli wrote:
> Some user had voicely complained me that one of thetir correspondent
> (say mario@??? -fictitious-) has all his e-mail rejected.
> I checked and turned that the server, that officially has the name
> mail.ditchedserver.org, send this helo:
> HELO ISCRA_domo.arsi
> (and this name is the real one that send !)
>
> my exim 4.63 is unhappy and reject immediately the connection saying there
> is an illegal (I suppose '_' )characther in helo name.
>
> This sound reasonably since all but that server that send with such headr
> send malware. However these users are veri upset and do not accept that
> our servve cannot accept such messages, while other servers in other
> istitutions accept without problem.
>
> Then i ask: is possible to skip, for a certain source IP, and for a
> certain set of recipient EVERY check, acceptin even the most malformed
> message ?
>
> In alternative: can some one give me a link to some offical rule saying is
> not acceptable sending Helo with underscores or non existant FQDN ?
>

Hello

quoting RFC2821 paragraph 4.1.2:
In
particular, the underscore character is not permitted. SMTP servers
that receive a command in which invalid character codes have been
employed, and for which there are no other reasons for rejection,
MUST reject that command with a 501 response.


If you wish to accept them, you can put in your config:
helo_allow_chars = _