Hello, I have been experiencing some strange things with mail delivery from a particular client. The client uses a gateway device in front of their Exchange system; this device is configured to do reverse lookups. When the gateway device contacts our external address at mail.somewhere.com at 123.123.123.123 my Exchange server responds with exch01.somewhere.com at 321.321.321.321. The device then discards the connection believing that the communication is bogus when in fact it is legitimate. I believe that it has something to do with my MX records and DNS, but I have not been able to effectively troubleshoot the issue. In a FE/BE configuration what MX records should I have in my DNS database?

On Tue, 13-Oct-09 00:31:46 GMT, Al_Stu34 wrote:>Hello,> has something to do with my MX records and DNS, but I have not been able to effectively troubleshoot the issue. In a FE/BE configuration what MX records should I have in my DNS database? When their server connects to your server your server responds with a'220' banner. In that banner is (typically) your server's FQDN.There's no IP address in that information (at least none is requiredand if some other server expects to find it there they'll have aproblem with just about every SMTP server on the Internet).If what you're saying is that the "A" record referenced by yourdomain's MX record has a FQDN different to the FQDN in the 220 banner,well, that's pretty normal. If you have more than one SMTP server fora single domain then each of them is likely to have a different namein the 220 banner.In your DNS you can have just one MX record that refers to a FQDN.That FQDN may be found in one, or several, DNS "A" records. Or you canerent FQDN. TheFQDN may be found in one, or more, DNS "A" records.In general, you should have the PTR record for the IP address seen byreceiving SMTP servers return the name of "A" record, and the "A"record should correspond to the FQDN presented by yoour server in the220 banner. This is, however, not a requirement, no matter how hardthe over-zealous admin of the other server tries to make it into one.All that's required is that there's a PTR record for the IP address.You may, however, be incorrect in the stating the type of test theother server is performing. They may be doing a forward lookup for theFQDN presented by your server's 220 banner. In that case you need tohave an "A" (or "MX") record foe exch01.somewhere.com in your externalDNS -- or change the name in the 220 banner to mail.somewhere.com.---Rich MatheisenMCSE+I, Exchange MVP--- Rich Matheisen MCSE+I, Exchange MVP

With SMTP, usually reverse DNS lookups are done at the receiving side, not when sending. Anyhow, you should double-check your public DNS record to make sure that the server's PTR (pointer) record has the server name mapped to the server's correct IP address.Jon-Alfred Smith MCTS: Messaging MCSE: S+M

Use the below tool and check for A record as well as DNS to make sure all in place http://www.mxtoolbox.com/DNSLookup.aspxVinod |CCNA|MCSE 2003 +Messaging|MCTS|ITIL V3|

Thanks a lot Rich. Your explanation put me on the right path. Alan

Great link! Thanks. Alan