Which to consider? Take a script/solution and put it on a dedicated server or take a remotely hosted solution (netmongol, zzn, i-p, bmb, enmail). # of estimated users ~ 10,000. Both webbased and POP3 support.

Depends on how comfortable you feel managing that many pop accounts. If you don't feel comfortable managing so many accounts, you should outsource.

10K is alot of users. I would consider outsourcing unless you have the skills to handle the weirdness that occurs at 10K. It would probably cost you less money to outsource with like a Critical Path at .90 cents a mailbox. You'd get webmail, IMAP and POP.

Just a though.