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Email domain hosted on 2 servers / issue with AD Contact forwarding

We have our email domain hosted on two mail servers. One is Exchange 2003 on a SBS 2003 box within our network and the other is MDaemon Mail Server hosted on a Windows 2003 Server in a remote public facing location.

The reason why is user cost based. Our central core of employees all have exchange based accounts and the rest are freelancers that have cheaper cost per user accounts on the remote server. Both servers are configured to process mail for our company email domain.. lets call it 'companymail.com' for now The mail flow is as follows;

All mail comes in via the remote MDaemon mail server. Any mail for accounts setup on this remote server get delivered at this stage, any unknown mail gets forwarded to the Exchange server. The exchange server then delivers any email it recieves from the MDaemon server to its accounts. I have set up an SMTP connector to route all outgoing mail through the remote MDaemon server.

As far as I could see, all was working fine untill I was asked to forward mail from an Exchange user (bill@companymail.com) to a user on the remote Mdaemon server (john@companymail.com). I entered a contact in AD and assigned it the SMTP email address john@companymail.com. Now when I sent a mail to bill@companymail.com it did not forward to john@companymail.com. I assumed that since I routed all email via the remote MDaemon server then it would forward ok. The undeliverable message I get back is;

"A configuration error in the e-mail system caused the message to bounce between two servers or to be forwarded between two recipients.  Contact your administrator."

Any help gratefully recieved!


1 Solution
Sorry to state the obvious and my apologies if you have already checked this but are you SURE that the address details on the contact created in exchange are correct.

By my reckoning, the MDaemon server should only forward the message back to the exchange server if the address is not recognised as a local MDaemon user.

I don't this is going to work.
To forward the email you need to send the email to an account outside of your domain.
By creating the mail enabled contact with an email address that matches your internal domain, Exchange gets confused. The address is now in its local database and it doesn't know what to do with it.

I don't like using the forward unknown recipient option for getting email to flow between two email servers.

The way I would do it is to have all email delivered to the Exchange server.
Then configure a dummy domain @mdaemon.domain.com for example and use an SMTP Connector to send email to that domain from the Exchange server. Configure @mdaemon.domain.com as an alias on the mdaemon server.
Finally create mail enabled contacts on the Exchange server for the users on the mdaemon server, with two email addresses, @mdaemon.domain.com and @domain.com - the @mdaemon.domain.com being the default. Exchange will accept email for the second domain and then promptly send it back out again using the SMTP Connector.

By having email delivered to Exchange you can also use recipient filtering which will cut down the amount of junk messages that the Exchange server has to process.


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