Email authentication (POPS before SMTPS)
In APOP before SMTP, the password used for authentication was encrypted, but the email text was not encrypted.
Although the risk of passwords being intercepted and the SMTP server becoming a springboard for spam is reduced, the risk of the user's email body being read still remains.
Therefore, POPS before SMTPS was conceived as a mechanism to encrypt between the user and the SMTP server.
With POPS before SMTPS, by enciphering the password used for authentication and the body of the e-mail together, the communication between the user and the SMTP server is completely encrypted and safe e-mail transmission is realized.