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As all mail things change I wanted to get some thought if checking PTR DNS records these days is advisable?

1) I do want to use it if it will actually bring benefit


2) I do need to keep false positives as close to zero as possible.

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AFAIK it is generally one of the standard anti-spam tests done by anti-spam suites such as SpamAssassin. It uses a weighting calculation to reduce the risk of false positives. It also recommends marking an email as spam (or rather 'possibly-spam') rather than deleting. I've also used a setup whether very high spam scores are deleted and others are flagged, which the email client can filter on delivery into a spam mail folder. – mctylr May 4 '10 at 15:03
up vote 2 down vote accepted

yes, checking of rev-dns is done by most of antispam deployments i've seen.

i guess like with other things [ eg. rbl ] - do not use it to take hard decisions, just add to a score of 'spamminess' counter and mark message as suspected only if general score goes above some limit.

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Also, I think you generally just want to check against the 2nd level part, not etc... – Kyle Brandt May 4 '10 at 13:14

I wouldn't use it to reject outright, but as stated to either weight a spam score or to greylist or some other action.

Also only check on "rdns present", I think you'd have too many false positives if you tried checking for matching forward/reverse dns.

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