Search Again: Re: I am a idiot, no wait, I just don''t know From: Men & Mice Support Date: Friday, April 4, 2003 Time: 4:52:21 pm At 6:38 PM -0500 4/4/03, Len Conrad wrote: >Furthermore, almost no, I would say no, mail servers reject mail if >the sending MTA's PTR hostname doesn't have a matching A record for >that hostname. We do this on IMGate/postfix, but ONLY for a few >selected @sender.domains where we know the PTR + A match exists. Len, I hate to contradict you, especially given that you do in fact know more about mail service setup than I do. But I have seen examples counter to what you state. Let me explain what I've seen. Two cases. Both can be avoided by having everything match. Case 1: Outgoing mail. The sending mail server identifies itself using a name other than the one in the PTR record. Suppose the sending mail server identifies itself as "mail.example.com", but the PTR record says "a-b-c-d.dsl.example-isp.net". Some mail servers will reject the connection. Case 2: Incoming mail. An SMTP relay server (i.e. someone else's outgoing server) receives a message for user@example.com. The relay server looks up example.com and sees this: example.com. MX 10 mail.example.com. mail.example.com. A 192.168.1.10 The relay server then looks for the PTR record for that address, and it finds: 10.1.168.192.in-addr.arpa. PTR 10-1-168-192.dsl.example-isp.net. Some relay servers will bounce the message right there. Otherwise, assuming any further DNS-based tests are passed, the relay will connect. But the receiving server may be expected to identify itself as 10-1-168-192.dsl.example-isp.net, not mail.example.com. Otherwise, the connection might be dropped and the message bounced. Neither of these cases is common. But they do both happen. ____________________________________________________________________ Chris Buxton Men & Mice support@menandmice.com Making DNS Easy

Messages In This Thread: Re: I am a idiot, no wait, I just don''t know by Men & Mice Support on Apr 4, 2003 at 3:24:03 pm Re: I am a idiot, no wait, I just don''t know by Len Conrad on Apr 4, 2003 at 3:38:46 pm Re: I am a idiot, no wait, I just don''t know by Scott Haneda on Apr 4, 2003 at 4:19:17 pm Re: I am a idiot, no wait, I just don''t know by Len Conrad on Apr 4, 2003 at 4:24:20 pm Re: I am a idiot, no wait, I just don''t know by Men & Mice Support on Apr 4, 2003 at 4:52:21 pm Re: I am a idiot, no wait, I just don''t know by Scott Haneda on Apr 4, 2003 at 5:04:31 pm Re: I am a idiot, no wait, I just don''t know by Len Conrad on Apr 4, 2003 at 5:41:26 pm Re: I am a idiot, no wait, I just don''t know by Men & Mice Support on Apr 4, 2003 at 10:36:26 pm