1.6 Applicability Statement

This extension is used by clients to support authentication to SMTP servers that implement the AUTH LOGIN extension. This extension is used by SMTP servers to provide an authentication method to control access to the SMTP service.

Since this extension does not encrypt the password sent over the network, it is only applicable to environments where a secure channel exists under the SMTP connection, such as Transport Layer Security (TLS), as specified in [RFC4346].