If you prefer a hosted, cloud based messaging (email) solution for convenience, you need to be aware of the dangers of some of the offerings out there:
"Yesterday, it was revealed that 10,000+ Hotmail accounts were compromised and all of the usernames and passwords of these accounts were posted online. It was a major security and scam issue, but it was thought to only affect Hotmail users."
If you want something secure, check out LotusLive iNotes
, a SECURE, stable platform based on the long running Lotus Domino server platform. It includes built in virus/spam controls.
Built in instant messaging, charts, web forms, surveys, meetings, and more. All starting at around $3/month per user.