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Exchange 5.5 unauthorized mail relay

By jstajduhar ·
Our exchange server is being used as an unauthorized spam server - but it is not an open relay. The unidentified spammer is changing the FROM field to reflect their intended recipient (ie Bob@yahoo.com) then sending the spam to an invalid person onour server (ie xyz123@ourserver.com). What happens is our server bounces the mail forward to Bob@yahoo (not the spammer)with a non-delivery message along with the spam message. It makes it look like we sent the spam when actually we bounced it as a bad address, but instead of bouncing it back it goes to the substituted address in the FROM field. Microsoft had no solution... Any ideas?

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Exchange 5.5 unauthorized mail relay

by Mully_MCSE In reply to Exchange 5.5 unauthorized ...

Check your settings on the IMS connector. Select the routing tab on the IMS connector properties. Click the Routing Restrictions button and select the top box (Hosts & Clients that successfully authenticate). You'll need to stop and start the IMSonce you have made this change.

Hope this helps.

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Exchange 5.5 unauthorized mail relay

by jstajduhar In reply to Exchange 5.5 unauthorized ...

Poster rated this answer

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Exchange 5.5 unauthorized mail relay

by brasslet In reply to Exchange 5.5 unauthorized ...

An excellent article on the subject of fully securing your Exchange server from these kinds of 'attacks' is at http://www.exchangeadmin.com/Articles/Index.cfm?articleid=7696. It discusses the problem you're having.

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Exchange 5.5 unauthorized mail relay

by jstajduhar In reply to Exchange 5.5 unauthorized ...

Excellent article - thanks!

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Exchange 5.5 unauthorized mail relay

by jstajduhar In reply to Exchange 5.5 unauthorized ...

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