60,000 mailboxes w/ WebAccess

[Will Froning]

I have a project floating in the wind for setting up an Alumni mail
system with web-access (eventually plugging into a portal solution). 
The max number of mailboxes would be 60K with 39K initially.

So I ask the FreeBSD-ISP community, what would you suggest?

Requirements:
IMAP/IMAPs
POP
Web-Access
Support 60K users

I'm thinking 4 Dell 1750s (2 webmail/portal servers and 2 IMAP/POP/SMTP
boxes) and a NetApp backend for the mailstore.

What would you suggest for the software?  imap-uw? Sendmail/Postfix?
I've used squirrelmail and imp.  I also saw GatorMail which looked super
nice.  Any suggestions welcome.

Thanks,
Will

-- 
Will Froning
Unix Sys. Admin.
wfroning at uop.edu