Re: Site policy vs. HELO

>     [QUOTE RFC2821 SECT 7.7]
> 
>     In recent years, use of the relay function through arbitrary sites
>     has been used as part of hostile efforts to hide the actual origins
>     of mail.  Some sites have decided to limit the use of the relay
>     function to known or identifiable sources, and implementations SHOULD
>     provide the capability to perform this type of filtering.  When mail
>     is rejected for these or other policy reasons, a 550 code SHOULD be
>     used in response to EHLO, MAIL, or RCPT as appropriate.
> 
>     [END QUOTE]
> 
> So, the question: Is this a valid interpretation of Sect. 7.7 -- 
> i.e., may an MTA provide a 550 response to HELO where it would 
> otherwise have given a 250 response to an EHLO if the site policy for 
> that MTA forbids HELO?

no.  7.7 is about third-party relaying, not about differentiating between
EHLO and HELO.  

Differentiating between EHLO and HELO for filtering purposes is a Really 
Bad Idea.  We have longstanding practice that HELO is a valid way to send
mail that doesn't need some ESMTP feature, and a lot of legitimate mail
is still sent using HELO.  Even if it were found that at the present time,
HELO vs. EHLO had some correlation to spam or viruses, the perps would
quickly adapt to any filters that tried to differentiate between the two.

Keith