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    Exchange 5.5 unauthorized mail relay

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    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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