Today I had to create a new email account for someone who was overtaken by spam. All it takes is signing up on the wrong webform and look out. Concentric Groupware provides email security by stopping spam, viruses, DOS attacks, phishing schemes, etc. by protecting your perimeter. All of the protection is on their servers so you never have to worry about updating or patching software. You just continue to use your existing email infrastructure such as MS Exchange and they merely analyze your incoming mail before passing it on to your internal mail server.
CTS also provides DNS hosting and groupware tools for team collaboration. I will check those out later.