Re: [exim] Forbid HELO

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Author: Beber
Date:  
To: Tim Wilde
CC: exim-users
Subject: Re: [exim] Forbid HELO
Le jeu 26 oct 2006 16:59:28 CEST, « Tim Wilde » à écrit :

> Dennis Davis wrote:
>> Exim won't advertise SMTP service extensions -- SIZE, 8BITMIME,
>> PIPELINING, STARTTLS, HELP, AUTH, etc -- in response to an HELO
>> greeting[1]. Any subsequent attempt by the client to offer AUTH
>> should be rejected.
>
> [ cut ]
>
>> [1] I strongly suspect that this is because HELO handling is still
>>     governed by RFC 821 which didn't know anything about SMTP
>>     service extensions.

>
> No need to suspect, that's exactly the case. HELO starts an SMTP
> session. EHLO starts an ESMTP session. AUTH is an ESMTP service
> extension, and is invalid under a standard SMTP session. Hence it is
> impossible, with an RFC-compliant server such as Exim, to have an
> authenticated session that started with HELO:
>
> 220 krellis.org ESMTP Exim 4.63 Thu, 26 Oct 2006 10:56:34 -0400
> HELO there
> 250 krellis.org Hello c-24-7-159-110.hsd1.ca.comcast.net [24.7.159.110]
> AUTH PLAIN sldkfjsdfksdf
> 503 AUTH command used when not advertised
>
> I would have to agree with Philip and the others on this thread, I don't
> exactly understand why one would want to block HELO itself, and this
> would be an RFC violation if done on a public mail server.


I agree too, but I get HELO connection only by spammers, and this
could help me to reject some of spam.

I also don't want that somebody bypass an identity of another using
that method.

> If it's
> being done on a private system where the OP can be sure that the only
> servers that (legitimately) connect will be able to speak ESMTP and
> start with EHLO, they can block HELO in the HELO ACL, it just seems
> somewhat pointless.


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