SpamAssassin has a feature to blacklist and unblacklist certain e-mail addresses. But recently I noticed something interesting that may need some more investigation. I have all addresses for domain example.org blacklisted, but also unblacklisted certain functional addresses as is shown in the example below.
blacklist_from *@example.org unblacklist_from abuse@* unblacklist_from hostmaster@* unblacklist_from postmaster@* unblacklist_from security@* unblacklist_from webmaster@*
Now I expected that firstname.lastname@example.org was going to be unblacklisted, meaning the mail would have both a spam score of both +100 and -100 making it effective 0 again. This modification resulted in a spam score of +100 and makes me worry that unblacklisting will demand that the domain part needs to be specified instead of having a wildcard. This will require some more testing in the near future, but for now, it may affect other installations.