SMTP Service Extension for Secure SMTP over TLS
Document describing the negotiating and upgrading plain socket connection to secure socket connection.

SSL & TLS
RFC's, drafts, and relevant documents of SSL and TLS in Japanese and English

SSL encryption check
Access this frameset to test if your browser supports TLS/SSL, and for a report of which cipher and key length is used.

SSL Version 2 Protocol Specification
Superseded by SSL Version 3 and TLS, but implemented by most browsers and secure servers.

The SSL Protocol Version 3.0
The SSL protocol specification. (Netscape)