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Recipient Lookup

Printed From: LogSat Software
Category: Spam Filter ISP
Forum Name: Spam Filter ISP Support
Forum Description: General support for Spam Filter ISP
URL: https://www.logsat.com/spamfilter/forums/forum_posts.asp?TID=5627
Printed Date: 16 July 2025 at 10:28am


Topic: Recipient Lookup
Posted By: swaber
Subject: Recipient Lookup
Date Posted: 25 May 2006 at 8:00pm
I see there is a way to White list Recipients but that seems to bypass all of the SPAM checking rules. I’m looking to see if there is a way to look up recipients either via static list or AD LDAP query and reject unknown recipients with a 550 and tar pit the sending mail server for additional request before running the various SPAM tests on the message. I don’t want to waste time and resources running the SPAM rules on messages for unknown recipients, and I want to prevent DNR load on our mail servers by 550ing the message at the gateway. I find that a very large part of our SPAM is destined for invalid addresses, and tar pitting would prevent concerns over directory harvesting.

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Scott Waber, MCSE, CCNP
Systems Administration Specialist
City of Las Vegas


Replies:
Posted By: LogSat
Date Posted: 25 May 2006 at 8:18pm
Absolutely yes! You can use the "Authorized TO" email whitelist.

If you have an "Authorized TO" list, SpamFilter will only accept an email address if it is in that list. Any attempt to send an email to a recipient not on that list will cause a 550 error, followed by an immediate forced disconnect of the sender (preventing them from attempting dictionary attacks by trying multiple addresses...).

The file containing the "Authorized TO" entries is continuosly monitored for changes (as are *all* configuration files in SpamFilter). If the file is modified outside of SpamFilter, it will be automaticllay re-imported within 60 seconds. This allows you to simply export a list of your users with any schedule you like. SpamFilter will automatically reload it every time.

As a side note, every time SpamFilter rejects an email because it is spam, it will always do so by sending a 5xx error to the sender, which, as you probably guessed already, means that SpamFilter will never send an NDR itself, thus saving bandwidth and resources. The only time SpamFilter sends an NDR is if accepts a "good" email, but then encounters problems when trying to forward it to your SMTP server (as in "mailbox full", "non existent user" etc.). In this case SpamFilter does have to notify the sender, and will have to send them an NDR.




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Roberto Franceschetti

http://www.logsat.com" rel="nofollow - LogSat Software

http://www.logsat.com/sfi-spam-filter.asp" rel="nofollow - Spam Filter ISP

Posted By: swaber
Date Posted: 25 May 2006 at 8:29pm

Ok, thank you. I was confused the term White list with all of our other mail products implies any address in the list will be exempt from testing and all messages will deliver to that address. I did not realize that it would still run the rest of the rules.



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Scott Waber, MCSE, CCNP
Systems Administration Specialist
City of Las Vegas


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