Email server recommendation

[Richard McNeilly]

I am trying to plan a ISP deployment using FreeBSD.  I am more familiar 
with Linux but during my research, it's been pointed out that FreeBSD is 
the more stable and reliable choice for an ISP.  Especially as an email 
server.

What is the best way to manage the addition of new users to the email 
server?  local users or is there a database solution.  Also is there a 
software package available to easily administer email accounts or does 
it all have to be done with custom scripts.

I would welcome any suggestions of anecdotes of experience.

Regards,
Richard