I'm using InoculateIT and haven't had any virus get through yet. A friend of mine suggested it to me who has been using it for quite along time, and he's never been hit by a virus either.
I really like it, it's not a resource hog, does the mail thing, and ofcourse the price is perfect

. I like the idea behind the people who make it, and they're right. Basically they think an AntiVirus prog should be just as much a part of your system as is your O/S. (e.g. you by a car and it comes with the doors, there for, an AV prog should come with any computer).
They also update the virus definitions very frequently and rapidly to protect against the newest thing.
Give it a shot, can't hurt.