I just upgrade to v8 and wanted to start using the reverse DNS lookup, I am
finding that this is blocking a lot of email that I need to get through.
In our tests, about 20% to 40% of legitimate E-mail is sent from a mailserver with no reverse DNS entry (oddly enough, probably about 1/2 of them have admins that swear that they do have a reverse DNS entry!). It just isn't safe as a spam test. For our Declude JunkMail customers, we recommend that they do not block E-mail based on that test, but instead use it towards the weighting system.
Currently I had to turn this feature off, but wanted to know if *not* having a reverse DNS entry is against RFC compliance?
Technically, yes (depending on your interpretation of the RFCs). However, there are lots of smaller ISPs that don't understand reverse DNS, and a couple large Internet providers that don't set up reverse DNS entries unless asked.
And on that note from your experiences am I blocking enough spam by doing that lookup to justify my battle with all the complaints when messages aren't being delivered?
Didn't you see our post earlier today? :)
About 38% of the spam to our spamtraps came from servers with no reverse DNS entry. Combined with the 20%-40% of legitimate E-mail that is caught, it makes for an extremely lousy test. However, we believe it is useful -- and keep trying to get legitimate mailservers to get reverse DNS entries.
-Scott
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