POP and POPs problems

Hi I'm running an E-mail server that that peoples dial into to get their mail. Well the last days peoples that's been dialling in haven't been able to get connected to the POP3 server without using a secure SSL connection. Well since this slows things down quite a deal over a slow connection I want to be able to have them connect trough the regular POP-server. Where and how can I change these settings?     Mr. Glenn H. Stava New Tribes Mission