Zimbra is a great mail server replacement for Exchange.  When you install Zimbra it suggests that you do not install a firewall...well, that sounds like they want their program to work at your expense.  Anyway, here is a firewall that I am currently using that works fine.   Note as an administrator you can limit access to the Administrator port which is a good idea as well as I often limit access to the web interface as well.  The firewall has a ...

Distribution List The Distribution List is a list of users that you can use to send mail to at one time. Instead of having to use CC: or BC: you can have a permanent list to send to. This is a great way to send company mail to one user and it is distributed to the entire staff. When you want to create a new list choose “New” ...