Gmail and the PBL


Yesterday I wrote about the underlying philosophy of spam filtering and how different places have different philosophies that drive their filtering decisions. That post was actually triggered by a blog post I read where the author was asking why Gmail was using the PBL but instead of rejecting mail from PBL listed hosts they instead accepted and bulkfoldered the mail.
The blog post ends with a question:

For those readers that know Gmail uses Spamhaus, I’d love to hear why Gmail couldn’t be transparent about its use.

I tried to post a comment, but it seems to have been eaten and never showed up on the post.
I don’t think this has anything to do with Gmail attempting to hide their use of outside blocklists. Rather, their technology is simply better suited to accepting and filtering after the SMTP transaction. Setting up a MTA to reject with different bounce codes for different reasons and notifying the sender of why can be a challenge for some.
Gmail’s philosophy is to accept all mail they can then filter it at the mailbox level. This philosophy drives both technology and system architecture. Trying to shoehorn in a different kind of filtering may be difficult or impossible without major changes. Then there’s the issue of maintaining a filter that is non-standard for the business. It makes perfect sense that Gmail sticks with their philosophy and filters mail from a PBL listed host.

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  • I don’t think it’s a technological limitation. I think it’s entirely philosophical on gmail’s part.

  • On other occasions, Google has indicated that they don’t trust 3rd party data & thus want to have their own technology look at the messages as well. This behavior is perfectly in line with that philosophy.

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