Asahi Net : Internet Software Guide
What is APOP?
APOP stands for Authenticated Post Office Protocol. With APOP, when your email software requests your email be downloaded from your Asahi Net mailbox, your password is encrypted for authentication. Because of this encryption, the level of security with APOP is higher than with POP. We recommend APOP, especially for users of wireless LAN networks or those connected to a connection service not offered by Asahi Net.