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Outbound spam filtering for forwarded mail

  • Scenario: forwarding email addresses from the Cloudron domain to 3rd party email services such as GMail

    Problem: when SRS rewrites the email headers to allow the mail to be classified as legitimately from the forwarding Cloudron host, it can also cause the forwarded spam to appear to be sourced from that host, resulting in it being blacklisted.

    Potential solution: implement adequate spam filtering for forwarded mail, for which no manual classification can be used to training a filter as could be for a local mailbox

    Another possible solution in the case of GMail might be to implement POP3 and allow GMail to pull mail from that. GMail no longer supports arbitrary IMAP servers since releasing its newer "Gmailify" service.

    See the original discussion here:

  • Personally, I'm migrating away from GMail, and wouldn't recommend it, although I appreciate it's difficult to cut those ties for some.

    Another possible solution: would be to forward to any other email service that does support POP3 but doesn't have spam filtering. That way, you're not sending email to GMail, it's pulling and filtering. Appreciate that a 3 mailserver setup is odd though, but then so is GMail.

    I think it's worth just having a POP3 post in Feature Requests though, purely as a way to allow for any other 3rd party email someone wanted to do this with. I can see privacy advantages in POP3 as well, if one didn't want emails stored on their Cloudron and just locally. I wouldn't like to see POP3 ignored as without advantage, when if privacy is a concern, that could be a legitimate use-case.

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