i think it's silly to have two, SSL and SRL. I can't think of a scenario where I would actually need two.
would this be one instance where I would use it?
let's say i hate ms. so i set to block @microsoft.com in the SSL. However, let's say i am on some sort of government board and still want to keep tabs on ms, so let's say somehow i don't mind messages that were cced to me or bcced to me from ms. so would this mean i do a SRL @microsoft.com?
the result is, anyone who at microsoft who sends email directly to me, will be blocked, however, if it's a distrubition list that's bcc or cced to me, i'll accept?