On Fri, 21 Feb 2003, 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).

Greywolf: do you mean unresolvable IPs or answers that don't have a period
"." in them?

You can use TCP Wrappers (/etc/hosts.allow) to disallow sendmail
connections from hosts whose name is unknown (or if reverse lookups return
a hostname that has a different IP than the original).

I haven't heard of a rule checking for a FQDN. (Maybe some milter rule to
check syntax of returned hostname.)

This is the wrong list for this discussion. A sendmail list would be
best, but if using a netbsd list maybe use netbsd-help or netbsd-users.
(current-users is for discussing building -current.)

   Jeremy C. Reed
   http://www.reedmedia.net/