Multiple Exchange 2007 servers at different sites having issues delivering email


I have 3 exchange servers.  2 in London(NLB) and 1 in Singapore.  they are on same domain connected via wan.  active directory sites and services seem to be setup ok.

we have the domain mx record pointing to london.  emails arrive fine to users who have a mailbox in london.  If a user in singapore who's mailbox is on the singapore exchange server has an email address with this domain, sometimes the emails flow through fine, and sometime the queue builds up.

When i look at the queue viewer on the london server it shows

Devlivery type:
SMTP Relay to Remote Active Directory Site


Message count:

Last Error:
451 4.4.0 Primary target IP address responded with:  "421 4.3.2 Service not available, closing transmission channel."  Attempted failover to alternative host, but that did not succeed.

If i reboot the Singapore server, the queues will deliver when the server is backup.  But this only lasts for an hour or so.

also there is a local domain and that points to the Singapore server, and that works fine to local Singapore mailboxes.


Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

George SasIT EngineerCommented:
I would check the line latency and see if this works as intended.

Also when you see the queue building up, try to telnet to the port 25 (or custom port if you have a custome one) of the singapore server and see if you can connect to the SMTP receiver.

When you have problems relaying intern e-mail, can you still deliver to the ?
If yes then I guess you have two separate SMTP receive connectors, one for the internal and one for the external mailflow, or how is your setup regarding the SMTP send - receive connectors ?

Any suspicious events on the eventlog on the Singapore server ?
philipfarnesAuthor Commented:

when the queue is building up, from server in london can still telnet port 25 and send manual mail via the command line.  does not go in the queue.  it just seems to be the SMTP Relay to Remote Active Directory Site emails that get stuck in the queue.

there are separate receive connectors for each domain and the domain has no problems.

in the even log the only this is ssl cert errors. we use public ones and they are in date.  the only issue we have is that the server cannot find a cert for the load balance fqdn.


George SasIT EngineerCommented:
Regarding the SSL errors don't worry about it, as long as you don't use TSL you can ignore them.

What about the SEND connectors ? You did not mention  anything about this.

Is your DNS configured properly ? And are your Sites and Services configured accordingly with the necessary subnets ?
And if you only restart the "Microsoft Exchange Transport" service will the mails start to flow ?
Can you post the Send / Receive connector settings ?

I am thinking you might have some kind of DNS problem. As the error message states it tries to reach the other end of the pipe but it can't.
Have you enabled SMTP logging and try to look trough those log files and see if you get some more detailed information ?

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today

From novice to tech pro — start learning today.