You haven't mentioned -- is this your BIS email address, i.e. the one that has something like @o2.blackberry.net as part of it?
The first email address that I got for mine got nothing but spammed, it was useless the first day I had it and there's no spam filtering. Instead, what I did was (a) choose a random one that didn't have spam (worked so far!
, e.g.), then (b) set up an @yahoo.com email address and use that instead as my "blackberry email" via BIS.
At least (b) allows me to have better spam control (yahoo's isn't the best, but hey - it's something) and for whatever reason T-Mobile USA + @yahoo.com is extremely well performing, notification is instant and so forth. I still use GMail, but it doesn't seem to work as well as the Yahoo one.
(I also use that @yahoo.com one now with their SMS alerts, like hockey scores 'n stuff being sent to me)