Why do some messages get tagged with "SA:0(?/?)" instead of numbers?. SpamAssassins "spamd" daemon has a max e-mail size limit. If a message is larger than that size, it just returns with no score (as it skipped it). As such Qmail-Scanner has no numbers to report, so it uses "?" to show that happened. Also, if some error occurs within SpamAssassin, Qmail-Scanner returns "?" again - showing that SA couldn't do the job on that particular mail message. If you use softlimit to limit the max amount of RAM SA can use - that can impact this too.
Ну значит произошли какие то ошибки при обработке письма (Also, if some error occurs within SpamAssassin, Qmail-Scanner returns "?" again - showing that SA couldn't do the job on that particular mail message).