Re: [Asrg] RE: Wierd reverse DNS resolution might affect spam filters

[Claus Assmann <ca+asrg at esmtp.org>]

On Sat, Jun 24, 2006, doug campbell wrote:

> I'm not at all sure that this is a non-issue for those of us using 
> sendmail (it's nice to know EXIM users aren't bothered by this). Neither 
> sendmail nor libmilter do the necessary step to verify correctness of 
> the rDNS result that they pass to my milter code as the "hostname" 
> argument of xxfi_connect(). Either sendmail or libmilter (whichever of 
> these provides the rDNS value passed to a milter) should be the ultimate 
> place where any modifications to add verity go. Other milter makers 

As it has been pointed out before, sendmail does the "reverse" check
(for obvious reasons). You can access that information in your
milter, see the sendmail documentation (doc/op/op.*):

      ${client_name}
           The host name of the SMTP client.   This  may  be
           the  client's  bracketed IP address in the form
           [nnn.nnn.nnn.nnn]    for    IPv4     and     
           [IPv6:nnnn:...:nnnn] for IPv6 if the client's IP
           address is not resolvable, or if it is resolvable
           but  the  IP  address  of  the  resolved hostname
           doesn't match the original IP  address.   Defined
           in    the    SMTP    server   only.    See   also
           ${client_resolve}.


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