Forwarding and NDR's

Posted on 2004-10-08
Last Modified: 2008-02-01
I have 2 questions which may be related.

I am using Exchange 2000 on MS 2000 Server. The outbound mail is set to goto BT's smarthost ( The inbound mail path is a bit more complex. It first gets collected in a catchall BT pop mailbox, This is picked up by a third party pop collector and passed onto SurfControl (spam filter) which then removes the rubbish and forwards the mail onto the exchange server. The mail is then sorted to the relevant mailboxes.
The mail server has no routable IP address. It has a 192 internal address only. The pop collector is on a different server to the exchange and surfcontrol programs.

Problem 1.
When a message comes in to certain mailboxes, they are forwarded to an external address. For some reason, these forwarded (copied) mails do not get sent but end up in the admin box as a non deliverable.

Problem 2.
Some emails get sent to the admin mailbox as non deliverable but the message appears to be addressed correctly. Even if there are no CC's on the mail it can still happen. The mailbox recieved most messages with any problem but there are at least 2 or 3 account that regularly do not recieve a (what seems to be) properly formatted message to the correct address.

Any pointers about where things are going wrong would be greatly appreciated.

Simon Lown.
Question by:epssupport
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Expert Comment

ID: 12259703
Problem 1
Test DNS resolution on smart host and on exchange server for returned domains.

Problem 2
Try to isolate the problem:
Try smtp communication without using the spam filter, and so on
Cause right now you have 3 elements which may cause this problem, try to reduce this number

P.S. I just gave you basic troubleshooting steps, if some-one had an exact same problem, he would be able to point you to the right place immediately

Author Comment

ID: 12259929
Problem 1

The DNS is not a problem on smarthost. All emails sent from desktop go without any problems. It only seems to be forwards that are an issue.
Unless forwards use a different route to standard mail I think DNS can be ruled out of the equation.

Problem 2
Not sure how I would reduce the elements on this. I suppose I could remove the spam filter (surfcontrol) but I'm fairly sure that's not where the problem lies. It's been installed for quite a while and it's only since switching to BT broadband that this problem appears to have come up. (Could be a red hering (BT), we have recently added quiet a few new users and they appear to be the ones mostly affected. (Possibly another red herring)
I don't think the fact the switching to BT or newer users seem more affected is really where the problem lies. Could be wrong but I just don't see how that could be. (Spose that's why I posted the questions in the first place.)

I will try removing surf control from the mix over the weekend. Meanwhile, any further ideas appreciated.


Expert Comment

ID: 12260488
First, if you use forwards e-mail as a normal e-mail, does it work ?
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Author Comment

ID: 12293306
Unfortunately, the isses I was having with exchange are now no longer relevant. I did manage to resolve the first problem, it was duplicate mail addresses in the contacts for forwarding the mail. The contact had picked up the same domain addresses when they should only have been an SMTP external address. Sorry I did give you the error code from the mail on that. Probably would have got it right away.
However, I have since had a RAID array go down and since we couldn't recover the array, backup tapes were needed. However, the little darlings that were responsible for tapes hadn't bothered for the last six weeks.
Now I have a whole bunch of new issues relating to disaster recovery in exchange 2000.
I will start another thread to pose these questions.

Thanks for the help with the above.

Accepted Solution

v_alber earned 500 total points
ID: 12297651
No problem

Author Comment

ID: 12303730
Would you believe it. I have rebuilt the server and have managed to salvage the mail from an older backup using just the database files and the AD from a server that was in the same domain. It does however seem that the problem with forwarding mails is still an issue.
The setup is somewhat simplified in that I have not installed the surfcontrol software yet so mail comes from pop account via third party software and straight into exchange 2000.
I did notice that the SPAM we were getting was trying to forward to lots of other mailboxes. From 1600 messages we had 400,000 mails with non routable addresses. YES 400,000.
Obviously I deleted them but this makes me think that there is a routing setting here internally in exchange to stop SPAM that is also affecting a genuine forward. I have Disallow Public Folder Referals ticked. Is there something I need to set to allow genuine forwards with this option switched on?
Any clues please.


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