On Tue, 7 Mar 2000, Ian Southam wrote:
> > 421-Reason: domain name verification of your mail server´s
> > 421-IP address [195.88.44.1] has failed.
> > 421-This is often caused by missing or inconsistent DNS reverse records.
> > 421 Please check with your DNS administrator.
> > QUIT
> >
> > Is this political correct?
>
> It is a common anti-spam measure and, if your mail server does not reverse
> lookup (or reverses wrongly) a lot of sites will refuse mail.
>
> That said, there is no rfc I know of that mentions this behaviour as being
> OK.
RFCs on the whole define how hosts must behave if they want to interwork
with each other. No host is *required* to interwork. That's a matter for
each host's management. However, RFC 2505 (Anti-Spam Recommendations for
SMTP MTAs) does mention blocking hosts based on their DNS names, but
doesn't mention the specific case of an address not reversing.
--
Philip Hazel University of Cambridge Computing Service,
ph10@??? Cambridge, England. Phone: +44 1223 334714.
