We have had Nortons on our desktops and servers for years. I don't care for it. We have had two incidents where they posted virus definitions that didn't work and we were infected despite having the latest updates. However, since you have Antigen, that will give you great coverage for your email server. We will be purchasing that product at the beginning of our next fiscal year and I will be glad to get rid of Nortons.
Karen List Charter and FAQ at: http://www.sunbelt-software.com/exchange_list_charter.htm