1. Stunnel is a socket wrapper which can provide SSL (Secure Sockets Layer) support to ordinary applications. For example, it can be used in conjunction with imapd to create an SSL secure IMAP server. From Redhat 8.0 RPM

2. Universal SSL tunnel for network daemons The stunnel program is designed to work as SSL encryption wrapper between remote client and local (inetd-startable) or remote server. The concept is that having non-SSL aware daemons running on your system you can easily setup them to communicate with clients over secure SSL channel. stunnel can be used to add SSL functionality to commonly used inetd daemons like POP-2, POP-3 and IMAP servers without any changes in the programs' code. From Debian 3.0r0 APT