Exchange 2007 mail delivery problem - Delayed mail to some recipients
Posted on 2010-09-01
I have a very peculiar problem, some of our outgoing mails are delayed and the users
get delay notifications. So far, nothing unusal...but...
- Only mails to domains that use Softcom.dk as mx are delayed, no matter what the
domain is (softcom is a antispam service). All other mails are delivered propperly.
10 deframx10.softcom.dk 126.96.36.199 5 min SMTP Test Blacklist Check
10 dkcphmx32.softcom.dk 188.8.131.52 5 min SMTP Test Blacklist Check
10 dkcphmx46.softcom.dk 184.108.40.206 5 min SMTP Test Blacklist Check
- Only some of the mails to theese domains are delayed, i.e. 80% of the emails are sent
without any problems, 20% are delayed ca 15-25 hours and the users get delay reports several hours later.
- All other mails to all other domains are sent properly.
More info about our servers:
- The problem affects several of our servers, on different domains, all SBS2008.
- The servers have different internal IPs and different External IPs, none are dynamic or residential IPs.
- All the servers use the same firewall (Draytek)
- Our servers are not blacklisted, reverse DNS is ok.
- mails to the affected domains are delivered ok if we use Telnet - no problems to connect to softcom.
- SMTP Logging is on - when a mail that is delayed is sent - there is nothing in the SMTP log about it - like the server not even tries to send it.
- When the same delayed mail is sent/delivered 20 hours later the SMTP log shows a normal delivery.
Any suggestions what might be the problem?