SpamAssassin

# URI with only http (no https)
uri_detail      HTTPONLY raw =~ /^http:/
describe        HTTPONLY no TLS
score           HTTPONLY 2

# first catch all posts and give them 3 spam-points
header          NO_TLS  Received =~ /from.*by <your SMTP hostname>/
describe        NO_TLS  no TLS in SMTP
score           NO_TLS  3

# then honor the ones using TLS
header          TLS Received =~ /using TLS.*by <your SMTP hostname>/
describe        TLS TLS in SMTP
score           TLS -3