Re: [Exim] helo_verify

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Author: Philip Hazel
Date:  
To: Weavind, Mike, Exim Users Mailing List
Subject: Re: [Exim] helo_verify
On Thu, 21 Nov 2002, EXIM Users wrote:

> We are looking at version 4 but reading the docs for that suggets it also
> does a whole string match. Looking at the code I guess it wouldn't be too
> difficult to hack. Has anyone else done this already?


If you really want to do this, there is perhaps no need to hack. In Exim
4, use helo_try_verify. In the ACL you can test whether verification
worked or not. If not, you can look at the value of $sender_helo_name
and apply whatever rules Exim permits. The dnsdb lookup would allow you
to look up MX records.

However, as Greg Woods says, this is misguided:

On Thu, 21 Nov 2002, Greg A. Woods wrote:

> Yup, because what those servers are doing is flat-out not allowed by any
> SMTP-related standard. The greeting name _MUST_ be the principal
> hostname for the client. The whole idea is to clearly and uniquely
> identify the client _host_, not it's sub-domain. This has been a
> fundamental absolute requirement of SMTP for only about 20 years now.


Absolutely!

--
Philip Hazel            University of Cambridge Computing Service,
ph10@???      Cambridge, England. Phone: +44 1223 334714.