I have got a private server running postfix, spam-assassing, dovecot, sieve... a common deployment on a linux server, but my SPAM filter doesn't work very well, because my client "set" is reduced and spam emails are like ten times bigger than my ham mails.

I could of course catch any spam collection freely available on the Internet to use as learning set for my spam-assassing filter, and my own gmail ham mail as ham set, but anyway, I don't think it will work reliably because I have to access to enough mails to have a well-training spam-assassing filter.

I think of three solutions:

  • Is there any well-trained spam-assasing filter available on the Internet? I could take one and pass to my spam-assassing filter, replacing the current one.

  • Take every mail I receive from my server, and forward them to a gmail account created ad-hoc with that purpose, and see to which folder arrives. If it arrives to a SPAM folder, I just simply send the original mail to the SPAM folder of my customer. If it doesn't, then to the cur directory. Creating a tiny imap client to do that shouldn't be too hard to code. All of it, provided that I don't forward too much emails to gmail, for example, discarding emails from compromised accounts and so on.

  • Same idea, but instead of simply do a double-forwarding (first to gmail, then to my customer), forward them separately (without waiting for the gmail results), but use the gmail results to train my own spam-assassing filter periodically (each day, for example). In that case, spam-assassing, theoretically, should mimic slowly the gmail filter.

The think is I don't dare to use gmail for that non-intended use, but I don't know exactly how to move on to improve my spam-filter otherwise.

closed as off-topic by Esa Jokinen, Jenny D, MadHatter, mdpc, quadruplebucky Jun 16 '17 at 7:19

This question appears to be off-topic. The users who voted to close gave these specific reasons:

  • "Questions should demonstrate reasonable business information technology management practices. Questions that relate to unsupported hardware or software platforms or unmaintained environments may not be suitable for Server Fault - see the help center." – MadHatter, quadruplebucky
  • "Questions on Server Fault must be about managing information technology systems in a business environment. Home and end-user computing questions may be asked on Super User, and questions about development, testing and development tools may be asked on Stack Overflow." – Esa Jokinen, mdpc
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  • 3
    If you forward a bunch of spam to Gmail, they will quickly blacklist your IP address, making the whole exercise pointless. – Michael Hampton Oct 24 '16 at 14:23
  • Yes, you're right. Questions updated (let's suppose I control from the server-side the emails I pass to gmail to avoid suspictious activity). – Peregring-lk Oct 24 '16 at 15:20

If you just forward your mail to Gmail without removing your IP, there is a big probability that your mail will be considered as spam. If the sender is using SPF on his domain, gmail will verify that and see that the IP sending this email (your IP) is not in the SPF records. If yes, it will reject or classify this message as spam. And your test will not be useful. In this situation a POP collector from Gmail could perhaps be more useful, but after that you need to verify in the gmail mailbox, if the message is in the main or spam folder.

Anyways a real on premise anti spam is really better.

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