We have just started monitoring this and the stats are a little low but when all servers have the anti-spam service in place we expect the average spam to run around 20% of our E-mail. What are you guys seeing?
We use Spamassassin runnign on our Linux mail servers. We have it dumping all the mail into each individual user's "Spam" box. This way they can log into via their webmail interface and see if there is any legitimate e-mail waiting for them. This way we are covered legally. If they do not log in after 45 days, the e-mail in the "Spam" box is automatically deleted.