Spam Assassin?

A site I run has started getting slammed with spam since I changed hosting companies. Both companies use Spam Assassin, but must have had it configured differently. Now it’s up to me to try to slow the flood. Anyone with their own domain familiar with it? The support wiki is geared toward server admins, not account admins, and so is no help.

On the configuration panel it list 5 as being “aggressive,” with higher number settings as “more conservative.” Does that mean it’s more conservative in what it blocks, or more conservative in what it lets through? I can’t tell from experimenting because the spam attacks are quite cyclical. Having them drop off may mean I moved it in the right direction, or it just might be coincidence.

I’m getting a lot of complaints about this, so any help would be much appreciated.