Dave and Matti, thanks for your ideas; they got me thinking/testing in some new directions, but I'm still pretty stumped.
Regarding the possibility of greylisting: "does the email deliver with the next queue run?" No. Our mail server makes 5 attempts over the course of several hours and usually all 5 attempts return the '450 busy' smtp response. Regarding our MX records: we are using a third party spam filtering gateway for inbound mail on some domains, but not all domains. I hadn't thought of this being a potential problem before. But I've specifically tried sending tests from domains that are NOT using the gateway and these still get the '450 busy' response. To add to the mystery, I've discovered that the connections aren't failing 100% of the time. The connections are failing roughly 95% of the time. About one out of every twenty attempts are delivered fine. When I try to telnet to att.net's smtp servers from our mail server (mail.addisontech.com), I get the exact same result: 95% of the attempts return '450 busy', while 5% connect fine. Telnet from my workstation (on a different IP address, but in the same Class C IP range) results in 95% failure (450 busy). Telnet from my home computer (through a completely different ISP) results in 100% success. Coupled with the tests Dave ran, I'm not sure what to make of these results. AT&T continues to assure us that our mail server IP is not being blacklisted. -Keith ---------- Original Message ---------------------------------- From: "Dave Doherty" <[EMAIL PROTECTED]> Reply-To: [email protected] Date: Tue, 28 Feb 2006 13:11:27 -0500 >ATT.NET's MX addresses are 12.102.240.23 and the one you tried to reach, >204.127.134.23. > >Dnsstuff.com says both are fine. > >When I telnet from my mail sevrer, they come up OK. > >When I telnet from my workstation, they both report the 450 error. > >I have PTR records on all IPs, so I am guessing they are doing some kind of >lookup to see whether the IP that is connecting has an MX record attached to >it. > >If you are gatewaying your inbound mail, then the MX record would not point >to your mail server. I would suggest telnetting from your gateway if you >have one to see if that is the answer. > >-Dave > > > > >----- Original Message ----- >From: "imail" <[EMAIL PROTECTED]> >To: <[email protected]> >Sent: Tuesday, February 28, 2006 11:45 AM >Subject: [IMail Forum] 450 busy, when delivering to att.net > > >> Starting about a week ago, all outgoing messages sent from our Imail >> server to any @att.net account have been failing delivery. Every time our >> SMTP server tries to connect to att.net or worldnet.att.net, we get the >> following error: >> >> 450 busy - please try later >> >> This ONLY happens when attempting to send to AT&T's mail server. We are >> delivering mail to other servers fine. We are receiving mail from >> @att.net email accounts fine. But we can reproduce this problem when >> sending from any of the domains on our mail server to any @att.net email >> account. >> >> We contacted att.net's mail administrators and were told that the problem >> must be on our end and that they would not help us. I'm stumped. >> >> I've included one complete example from our server logs below. Thanks in >> advance for any ideas or advice you can give me. >> >> Keith W. Schoenly >> Addison Technologies, Inc. >> >> ------------------------------------------------------- >> 02:27 16:52 SMTPD(00EF01BC) [151.197.165.4] connect 151.197.165.10 port >> 4980 >> 02:27 16:52 SMTPD(00EF01BC) [151.197.165.10] HELO kschoenl >> 02:27 16:52 SMTPD(00EF01BC) [151.197.165.10] MAIL FROM: >> <[EMAIL PROTECTED]> >> 02:27 16:52 SMTPD(00EF01BC) [151.197.165.10] RCPT TO: <[EMAIL PROTECTED]> >> 02:27 16:52 SMTPD(00EF01BC) [151.197.165.10] >> D:\IMail\spool\D748500ef01bce269.SMD 618 >> 02:27 16:52 SMTP-(041078BE) processing >> D:\IMail\spool\Q748500ef01bce269.SMD >> 02:27 16:52 SMTP-(041078BE) [x] looking up att.net in HOSTS and MX >> 02:27 16:52 SMTP-(041078BE) Info - Found att.net in DNS Cache >> 02:27 16:52 SMTP-(041078BE) Trying att.net (0) >> 02:27 16:52 SMTP-(041078BE) [x] Connecting socket to service <SMTP> on >> host <att.net> using protocol <tcp> >> 02:27 16:52 SMTP-(041078BE) Info - Found att.net in DNS Cache >> 02:27 16:52 SMTP-(041078BE) Connect att.net [204.127.134.23:25] (1) >> 02:27 16:52 SMTP-(041078BE) 450 busy - please try later >> 02:27 16:52 SMTP-(041078BE) SMTP_DELIV_FAILED >> 02:27 16:52 SMTP-(041078BE) >QUIT >> 02:27 16:52 SMTP-(041078BE) [E] didn't send "QUIT": connection >> aborted02:27 16:52 SMTP-(041078BE) rl-recv: connection aborted >> 02:27 16:52 SMTP-(041078BE) >> 02:27 16:52 SMTP-(041078BE) [u] closing socket (u) >> 02:27 16:52 SMTP-(041078BE) requeuing D:\IMail\spool\Q748500ef01bce269.SMD >> R0 T1 >> 02:27 16:52 SMTP-(041078BE) finished D:\IMail\spool\Q748500ef01bce269.SMD >> status=3 >> ------------------------------------------------------ >> >> To Unsubscribe: http://www.ipswitch.com/support/mailing-lists.html >> List Archive: http://www.mail-archive.com/imail_forum%40list.ipswitch.com/ >> Knowledge Base/FAQ: http://www.ipswitch.com/support/IMail/ >> >> > > >To Unsubscribe: http://www.ipswitch.com/support/mailing-lists.html >List Archive: http://www.mail-archive.com/imail_forum%40list.ipswitch.com/ >Knowledge Base/FAQ: http://www.ipswitch.com/support/IMail/ > To Unsubscribe: http://www.ipswitch.com/support/mailing-lists.html List Archive: http://www.mail-archive.com/imail_forum%40list.ipswitch.com/ Knowledge Base/FAQ: http://www.ipswitch.com/support/IMail/
