> On Fri, 24 Sep 2004 11:36:27 -0400 (EDT) "Dan Mahoney, System Admin" > > The person running 1.2.3.4 has NO CLUE what they are doing. > > 1.2.3.4 should RDNS to whatever the "hostname" value of that > > machine is. This should be the same as the HELO the machine uses > > when talking out to the outside world.
Bob Apthorpe replied: > No. HELO is only required to be a FQDN and to resolve to an A record. > It does not have to match rDNS nor does it have to match the hostname > of the actual server sending out the mail. It might not be required or an RFC-ish "SHOULD", but any mail server that HELO's as a name other than its FQDN is doing something very odd anyway. Dan's "should"'s are perfectly correct, and most well-behaved mail systems with properly-configured DNS records do exactly that. (Exceptions include the hosting server I administer at work, which occupies most of a /26 except for a few IPs. For some unknown reason, it periodically gets mixed up about which IP is its "real" IP, and starts initiating TCP/IP connections of all sorts from the highest aliased IP instead. Blech. The machine is otherwise very well-behaved.) -kgd -- Get your mouse off of there! You don't know where that email has been!
