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Reverse DNS fails on Spool Filtering
Problem reported by kevind - 5/12/2024 at 11:22 AM
Submitted
Here's a strange problem with Reverse DNS in Spam Checks.

Some messages will pass the "Inbound SMTP Blocking" but fail the "Spool Filtering" check.  Not sure how this could happen as it has the same sending IP.  A good example of a message this does this is the "Best of MSN" newsletter.

So for this reason, we have to disable "Spool Filtering" but would prefer not to so that we can include the Forward Confirm Fail and Mismatch scores.

Thanks.

11 Replies

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2
Brian Bjerring-Jensen Replied
Build?
2
kevind Replied
Good point. Running 8874 (Apr 18, 2024). Will upgrade to 8888 (May 2, 2024), but don't see any changes to Reverse DNS in release notes.
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Brian Bjerring-Jensen Replied
Are you caching the DNS replies?
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kevind Replied
Not sure. Where is the setting for DNS caching?

It's only with certain messages, so don't think it's related to caching. A message is received via SMTP and Reverse DNS passes, then less than 1 second later Reverse DNS fails during delivery.
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Jorel Haggard Replied
Employee Post
Kevin,

In Settings > Protocols, you should see the SMTP Out card: The first toggle at the bottom of the card will enable DNS caching. Let me know if this helps! 
Jorel Haggard System/Network Administrator SmarterTools Inc. (877) 357-6278 www.smartertools.com
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kevind Replied
Hi Joel, thanks for the help finding DNS Caching.  I'm not really having an issue with the speed of message delivery, so not sure this applies. Should it be enabled or disabled?

Plus, this is for SMTP Out and I'm not having an issue with messages going out. The problem message is one being delivered to user mailboxes.

On a totally separate note, your SMTP Out online help has this bullet:
  • Enable TLS if supported by the remote server
But just FYI, that toggle is not in the current version of SmarterMail. Maybe tell the person who maintains your online help.

Kevin
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Blake Blossom Replied
Analyze the configuration of Spool Filtering and see if you can adjust it to rely less on RDNS and focus more on other spam indicators like sender reputation or content analysis
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mh Replied
From my understanding older builds had some DNS issues because of .net framework, and moving to the .net core builds resolves some of this. We had the September 2023 release and had a lot of the same issues where incoming mail would fail reverse DNS lookups for the remote server, even though they definitely existed. Some days were horrible. Most of this seems to be better in recent builds.

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kevind Replied
OK, we're on build 8888 and still seeing this problem. Now occurring with eBay messages.

Reverse DNS passes during SMTP, but fails during Spool so the message goes to Spam folder. Turning off Spool Filtering fixes it, but then we lose the Forward Confirm Fail+Mismatch scores.
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Brian Bjerring-Jensen Replied
File a ticket for SM :)
1
kevind Replied
Good call. I was hoping they would respond here...

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