just curious if this site is going to be public or for a private group? managing all those pop accounts can be a pain sometimes. do you want to specifically give pop access to these users? or just email account they can use anywhere. there are other methods of giving free emails.
edit:
but more to your point, there is a perl script /scripts/addpop that cpanel uses to add pop accounts. you could slightly modify it so that instead of using <STDIN> to get the address and password, you use $ARGV[0] and $ARGV[1] to grab the email and pass so you could make system calls to the script and add the emails like that.
