The spam filtering isn’t particularly great out of the box - it’s the Debian shipped SpamAssassin, which is unlikely to catch much compared to commercial options.
It should however be writing headers to mails with the spam scores and other tracking information. Can you confirm if that’s the case?
To help improving the spam filtering, I train Spam Assasin with what I think is spam based on what’s in the Junk and Spam folders in any mailbox, I run the following command in the crontab:
Thank you for the cron job, I’ll definitely add that one.
This is interesting. I have a catchall email address. From what I can see, the messages to the existing email address are being being tagged with Spam headers, the messages directed to “non existent” mailboxes are not being checked by SpamAssassin.