On Fri, Feb 21, 2003 at 12:07:57PM -0500, Bill Chiarchiaro wrote:
> > Is there any way in sendmail to disallow incoming mail from a place
> > whose IP address does not map to a FQDN?
> 
> FWIW, this is easy to do in postfix (although I no longer do it; there
> are too many lazy ISPs who don't set up PTR records for legitimate
> customers  --- I'm depending more on spamassassin now).

I don't know of any way in sendmail without writing new rule sets.
There is also the milter capability which may be able to do it, but
I've never used it.  Sendmail passed my pain threshold just as
milter was introduced.

I also switched to postfix and currently use the restriction. My
operation is small enough that white listing is reasonable.  Only
about 5% of my unknown host rejects are legitimate. The rest are
either spews or open relays.

-- jay