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Reverse DNS Lookup

Posted on 2007-03-29
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Last Modified: 2008-01-09
How do i configure my exchange server (SBS2003) to use reverse dns lookup to block incoming mail like other servers do.  I'm looking to cut down on junk emial and i know this would help.
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Question by:tobiaspw
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LauraEHunterMVP earned 252 total points
ID: 18819644
Follow the steps in this tutorial: http://www.nemx.com/products/SecurExchange/howto/reversednslookup.html

Hope this helps.

Laura E. Hunter - Microsoft MVP: Windows Server - Networking

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by:Toni Uranjek
ID: 18819664
In properties of "Default SMTP virtual server" go to Delivery tab, click Advanced delivery and you will find checkbox "Perform reverse DNS lookup". This option is reported to slow down your server and there is another catch, are you sure that all your senders have proper PTR record, for reverse lookup to work correctly?

HTH

Toni
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by:Zenith63
Zenith63 earned 248 total points
ID: 18819723
Yes be warned reverse lookup blocking is fairly useless these days.  Most spammers are using home broadband packages which will now have proper PTR records pre-configured for them, while quite a lot of businesses don't have PTR records setup for their domain, generally because they don't realise it's important or don't know about them at all.

I've had a few conversations with the spam guys at MailMarshal (one of the main spam filtering softwares out there at the moment), almost all recommend not turning this rule on in MailMarshal (it's similar to the Exchange one).  When we have decided to turn it on in testing it tends to have very little effect at catching spam that the normal rules don't catch, but it sure increases your false positive rate.
To be honest I think this rule would run better in reverse, identifying servers without PTR records as legit senders instead of spammers :) .  Assuming you have some other spam filtering in-place of course...
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Expert Comment

by:mikebernhardt
ID: 18819827
This is something that if you can do if you upgrade to Exchange 2007:
http://www.openspf.org/News/2006-12-14

In Exchange it's called SIDF (Sender ID Framework)
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by:Computer101
ID: 20324298
Forced accept.

Computer101
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