If I give
sa-learn Maildir mails to train it as spam, it takes them without problems, but when trying to use a mbox file containing spam emails from my personal Gmail account (using https://takeout.google.com/settings/takeout/custom/gmail), it doesn't like it:
$ grep -c '^From ' spam.mbox 390 $ sa-learn --progress --no-sync --spam --mbox spam.mbox Learned tokens from 0 message(s) (0 message(s) examined)
So, it's clear that
spam.mbox contains emails (390 in fact), but for some reason
sa-learn decides to ignore them.
What could been going on here?