Symptoms: Since 31.8.2010 we have been having delayed delivery problems with our exchange 2007 mail server. The server is a Fujitsu Primergy TX200 running MS Server 2008 Standard and exchange 2007. One domain especially seems to be having trouble with our server. Their mail to us gets delayed randomly, and they receive error reports from their own mail server that our server is not responding: Their server is also.com and our server is mail.trefoil.fi -----Original Message----- From: postmaster [mailto:postmaster@gnt.fi] Sent: Tuesday, August 31, 2010 5:36 PM To: *** Subject: Warning: could not send message for past 4 hours ********************************************** ** THIS IS A WARNING MESSAGE ONLY ** ** YOU DO NOT NEED TO RESEND YOUR MESSAGE ** ********************************************** The original message was received at Tue, 31 Aug 2010 13:24:47 +0300 from: < ***@also.com> ----- Transcript of session follows ----- 451 4.4.1 reply: read error from mail.trefoil.fi. <***@trefoil.fi>... Deferred: Connection timed out with mail.trefoil.fi. Warning: message still undelivered after 4 hours Will keep trying until message is 5 days old This happens randomly, with no recognizable pattern. The mail gets delayed from a couple of hours to a couple of days, sometimes several mails per day sometimes per week. So far we don’t think any mail has been lost, only delayed. We haven’t encountered this problem from any other mail server than also.com, but it is the server with most traffic in our organization, so it might just be that the other ones haven’t been noticed. What we have tried: We have restarted all the hardware, and upgraded the firmware in all the hardware involved with our mail server. We have also checked all the firewall and spam-control black&white lists and everything seems to be in order with this, considering that all other mail traffic works without problems, and that the problem mail-messages always goes through, just delayed, leads us to believe that the problem isn’t connected to the firewall but that it is something strange with the exchange configuration. A big problem is also that we can’t get the problem to occur regularly, it happens randomly and when we have tried sending test-messages back and forth between the servers they have worked without problems. Please advice We are not sure how to proceed to find a solution to this problem, please advice what we can do to fix this, as we now can’t rely on our messages going trough.

Considering that all your other setiings whitelist etc is affecting the other compnay to send the mail to you. You can increase the smtp timeout on your Edge or internet facing server. Need to ensure and monitor as you are changing the default setting and may open up security. Please refer http://forums.msexchange.org/m_1800442922/mpage_1/key_/tm.htm#1800444520 http://technet.microsoft.com/en-us/library/bb232205.aspx .. also simi exchange 2007.

You have 2 mx records in your DNS Is exchange reachable on both IPs from outside? gnt.fi MX preference = 20, mail exchanger = mailgate2.gnt.fi gnt.fi MX preference = 10, mail exchanger = mailgate1.gnt.fi mailgate2.gnt.fi internet address = 192.130.190.90 mailgate1.gnt.fi internet address = 192.130.190.92 EDIT: Just checked myself. Can telnet to either of the IPs and get the same answer.

Hi, First you have to confirm the generating server of the NDR. From the error message, that seems the SMTP session has the issue between the source server and your Exchange server. This means the message was not accepted by your Exchange server. You can enable the Protocol Logging on the Receive Connector, then try to reproduce this issue and check the log, confirm the session is stopped in the SMTP phase. Thanks AllenAllen Song