Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!ncar!woods
From: woods@ncar.ucar.edu (Greg Woods)
Newsgroups: comp.mail.sendmail
Subject: Re: 5.65 use DNS cache?
Message-ID: <11950@ncar.ucar.edu>
Date: 26 Jun 91 20:46:48 GMT
References: <1991Jun26.194529.24019@mailer.cc.fsu.edu> <1991Jun26.203743.8902@mp.cs.niu.edu>
Reply-To: woods@ncar.UCAR.EDU (Greg Woods)
Organization: Scientific Computing Division/NCAR, Boulder CO
Lines: 13

There is a possible reason for thinking that sendmail isn't using the
DNS cache, and that is sendmail's insistence on checking MX records.
If there is an A record in the local name server's cache, but no MX,
sendmail will insist on querying the authoritative server to get an MX
record (or an authoritative response indicating that there is no MX),
thus appearing to "ignore" the locally-cached data. In this case
however, sendmail's behavior is correct, for the presence of an A
record does not guarantee that the proper thing to do is send the mail
direct. Lots of hosts (including all of our diskless workstations) have
valid A records but CANNOT receive their own mail, they are all MX'ed
to the appropriate server host.

--Greg