I know this is a shameless plug, but I'm a happy customer.
Have Inter7 do a SugarBox install for less time/money than
it takes to figure it out using online resources and googled
howtos. I didn't have to second-guess or debug anything.
Within 4 hours of the consultant logging in via SSH, I had
SMTP-AUTH, POP-before-SMTP, SMTP/SSL, POP3, POP3/SSL, IMAP,
IMAP/SSL, CRAM-MD5 and a complement of TinyDNS and SqWebMail
all working together. Within another hour, he had MySQL
replication and redundancy working. He left all the source
code on my box so that I could make modifications and
customizations later using "make install" and even build
additional servers later.
If you don't make a living installing Qmail/Vpopmail servers,
it's less expensive and more practical to just let someone
else do it. I've installed qmail/vpopmail from scratch before
and believe that it can be a PITA to get done right.