SSL works at the socket level. Sockets are a pair of end-points of a two-way communication link between two programs running on the network. All TCP/IP communication on the Windows platform uses sockets. In the email paradigm one of the sockets is used by the email client application and the other by the email server. These applications usually reside on different systems across the network, however there is nothing preventing them from being on the same system either. You can think of a socket as a data doorway into and out of an application. Normal email communications send your email messages out the door in a plain text format. As the message travels between doorways, it is susceptible to prying eyes. Electronic eavesdropping applications can easily read the contents of your messages as they travel across the network and gain access to attachments and other message data. SSL protects your messages by automatically encrypting the data as it travels between doorways (sockets). Data is automatically encrypted just before it goes out the door, and automatically decrypted immediately after it enters the door.