In addition to password-based authentication, Sun Java System servers support the authentication of users through examination of their digital certificates. Instead of presenting a password, the client presents the user’s certificate when it establishes an SSL session with the server. If the certificate is validated, the user is considered authenticated.
For instructions on setting up Messaging Server to accept certificate-based user login to the IMAP or HTTP service, see 23.5.3 To Set Up Certificate-Based Login
If you have performed the tasks required to set up certificate-based login, both password-based and certificate-based login are supported. Then, if the client establishes an SSL session and supplies a certificate, certificate-based login is used. If the client does not use SSL or does not present a client certificate, it will send a password instead.