Usually we've got heaps of spam daily say about 3,000 everyday including those have been filtered by free anti-spam software. We're planning to upgrade our system to Exchange2k7 but not sure if it's good enough handing spam. New anti-spam filter is quite costly that we can't afford (even though we've got charity license but most of the them are cost more than $3,000 per year).

Is there anyone knows if Exchange2k7 is good enough for spam or any cheaper anti-spam solution recommended?

Thanks heaps.