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.
POPS before SMTPS stands for "POP over SSL before SMTP over SSL". As the name "over SSL" suggests, encryption is achieved using SSL technology.
Email authentication (SMTP-AUTH)
SMTP-AUTH is an abbreviation for "SMTP Authentication", and is a method developed after POP before SMTP, adding a user authentication function to SMTP used when sending emails.
In POP before SMTP, since the SMTP server does not have an authentication function, the POP server authenticates instead and cooperates with the SMTP server to achieve the authentication function. Since there is no need to coordinate, you can send without first receiving the email.
SMTP-AUTH allows you to use different user IDs and passwords for POP and SMTP authentication. Although the operation management load is increased, security can be enhanced.
POP before SMTP remembered your IP address for a while and only accepted mail from that IP address. In other words, if you use the same IP address as the IP address you remember, there is a drawback that a third party can use the SMTP server.
With SMTP-AUTH, authentication is performed each time an email is sent, so you don't have to worry about such things.
In addition, Microsoft's "Outlook Express", "Windows Mail" and "Microsoft Office Outlook", which are used by many users, support SMTP-AUTH.
Email authentication (SMTPS-AUTH)
SMTPS-AUTH is an SSL-encrypted method of SMTP-AUTH. Encrypt between user and SMTP server.
The scope of encryption is only between the user and the SMTP server. Encryption between SMTP servers is not possible because all SMTP servers on the Internet must support encryption.
S/MIME is an encryption method that uses electronic signatures to send emails safely between users. By using S/MIME, you can protect your emails from threats such as eavesdropping, falsification, and spoofing.