Hi Arnold- Whether or not you will accept mail from an address without a (matching?) reverse record is usually an option on your mailserver software. In terms of outbound mail, AOL, for example will no longer accept mail unless the reverse is present. Some providers insist that it match, which makes things a little dicey if your mail server is handling multiple domains. I've gotten around that by wasting an ip address for each domain, and setting up the reverse records accordingly. Also, lots of folks are now verifying the validity of the sender to try to prevent spoofing the mailfrom. (although the spammers only have to spoof a valid email address to get around that) -Keith -----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu] Sent: Monday, April 05, 2004 5:03 PM To: NANOG Subject: Mailserver requirements Today I run across a MTA which refused to accept mail because it could not detect an MX record for the reverse mapping of the IP address of the server which tried to deliver mail. Is this correct? Or: if A is the IP Address of server trying to deliver mail, does mx(reverse(A)) have to exist? -- Arnold