Aaron,
In SME7pre3 POP3 is not an option in configuration dropdown box. The GUI only offers access to POP3 on the LAN (local networks). On the outside (public/Internet) networks POP3S is available. Using POP3S encrypts all transactions between the email client (Outlook/Thunderbird) and the server.
SOLUTION
The best solution is to change your email clients. Also, if your public clients are always coming from the same location on a static IP address you can simple add them to the list of local networks.
If none of that work, then you can open POP3 to the outside world, but realize this this poses a security risk. Login as root to the command line and enter the following commands.
db configuration setprop pop3 access public
signal-event email-update
Hope this helps.