We let spamassassin tag messages with 5 to 10 points; discards >10.
For “reasonable doubt” messages a user sees and can filter on a Tagged message.
Admins can study the report inserted
For the “no doubt” cases, we see only log entries:
2007-04-08 23:39:17 1Haf6Q-000M6I-Cd => blackhole (DATA ACL discarded recipients): This message contains malware (Trojan.Small-1604)
for malware, spam gets
2007-04-08 02:39:35 1HaLRE-000Kq0-3P => blackhole (DATA ACL discarded recipients): Your message scored 116.0 Spamassassin points and will not be delivered.