Backing/ Restoring an Exchange Server 5.

I have just finished setting up an Exchange server successfully. However, in my planning of my tactical approach to maintaining the server….I pondered on the process of backing and restoring the exchange server. What are the files that you must back up in order to perform a successful restore??? Where are the individual email boxes stored for each user on the exchange server????

I will be using Veritas’ Backup Exec to perform aformentioned backup/restore. Are there any “agents” needed to backup up open files?? How about the mailboxes themselves?? I don’t want to shutdown the email services everytime I schedule a backup.