At 08:35 AM 7/19/2004 -0400, Len Conrad <LConrad(_at_)Go2France(_dot_)com>
wrote:
As well PTR look up require at least additional 2 DNS requests, while
exists will require only one.
Most mail servers anyway do a PTR lookup on the connecting IP address
of course. postfix always does PTR and matching A queries, and logs when
the matching fails.
what about sendmail, qmail, exim?
I know the probably the most widespread commercial product IMail does not
do PTR queries, and that really sucks.
****************** REPLY SEPARATER ********************
Sendmail has the capability, but it was such a useless feature that I long
ago turned it off. At one point in the relatively short history of email,
it was quite a useful procedure. But the PTR resourse record has basically
outlived it's usefulness, and the blame for that lies squarely on the
shoulders of unresponsive upstream providers, and the difficulty in
configuring less than "C" class networks.
J.A. Coutts