Randy Warner said the following on 01/02/2007 03:55 PM: > The following recipient(s) could not be reached: > > Jack Hudler on 1/2/2007 12:45 PM > There was a SMTP communication problem with the recipient's > email server. Please contact your system administrator. > <synergy-gps.com #5.5.0 smtp;553 host is missing reverse dns > record (see http://www.internetmailserver.net/reverse-dns.html)>
Randy, some mail servers do a check to make sure that the IP address matching the name, is the same as the name matching the IP address -- it's called a reverse lookup. This is designed to reduce spam and spoofing; it's arguable whether it does much good. The problem is that often ISPs don't assign a reverse name unless you ask them. For example, one of my addresses (that I don't use for an external server) maps to: " [EMAIL PROTECTED]:~$ nslookup > mvfma.febo.com Name: mvfma.febo.com Address: 24.123.66.141 > 24.123.66.141 141.66.123.24.in-addr.arpa name = rrcs-24-123-66-141.central.biz.rr.com. " That would set off the warning you got from Jack's system because mvfma.febo.com doesn't have anything to do with rrcs-24-123-66-141.central.biz.rr.com. On the other hand, my mail server looks like this: " [EMAIL PROTECTED]:~$ nslookup > meow.febo.com meow.febo.com canonical name = febo.com. Name: febo.com Address: 24.123.66.139 > 24.123.66.139 Non-authoritative answer: 139.66.123.24.in-addr.arpa name = meow.febo.com. " Here, the two match so all is well. Usually, your ISP is willing to set up a "reverse DNS" record for your server that will provide a match, but you have to ask them to do that. Getting that record established should solve the problem reaching Jack, and possibly others who get mail through a server that does this check. Hope this helps, John _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
