I am always amazed to hear how much gets through on corporate systems. My wife works in a corporate office with a dedicated IT department and she says 60-70% of their total received is spam. I would think that number to be intolerable. For instance, I have a VPS and host about a dozen sites for small companies and non-profits and I am able to keep the received percentage below 10% using only spamassassin (catching 99+ percent). On three personal accounts (well known to spammers) I get a couple thousand spams per week. In the past week I've had two spams get through and one false positive. And the FP almost doesn't count because was borderline spammy and had a forged rcvd. I guess if you must have zero FP for a diverse group then you naturally have to give vermin a lot latitude, but I'd be cracking on the IT department pretty hard.
Mind you, that means that I'm missing a lot of spam - of those 11,000 emails that were left, probably half to three quarters were spam, but that's a lot better than they would see if they were with just about any other mail provider. (most hosting companies are CRAP for filtering).
