Personally, I don’t block spam. I keep receiving it because I find it interesting to study.
Where does it come from? Single IP? Single domain? Botnet?
Who does it target? list of harvested emails or specifically targeted?
Is it sent aggressively? Hundreds per minute or a few per hour?
What is it about? Meds? Gambling? Porn? Business deals? Visit a site?
Fake sender? valid or just random username with legit domain?
Fake subject? Trying to avoid spam detection?
Small body? Long body? With random chars to avoid checksum checking?
Imagespam? Distorted image?
Sent by professional spammers or amateur (Greek) marketers? :>
After all this, I always report is upstream using Spamcop (HabuL add-on).
I don’t have a mechanism to report it except if Exchange Server’s filters do this without asking me :)
Either way I don’t bother if this is happening without my consent because it’s helping the filters become better and more agile.
I’d love to analyze spam specimens but I do it only when they don’t get caught by our 2 stages filtering, and because time does not allows more dealing with them.
As an avg user I don’t have the vision a sysadmin has on the matter. I just block spam messages in order to avoid loosing time by deleting them manually.