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Exchange 5.5 unauthorized mail relay

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by jstajduhar

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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?

5 replies

by mully_mcse

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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