Instant Messaging server-to-server and client-to-server communications occur over TCP/IP. You can secure these communications by using TLS encryption.
Instant Messaging uses SMTP to send messages to offline users and for email archiving.
Browsers use HTTP to retrieve Instant Messenger resource files from the Web server. Once retrieved, the browser reads the HTML and displays the contents of the files. Client-to-server communication can take place over HTTP/HTTPS/SOCKS proxy. Also, HTTPBIND is a server component (that uses the HTTP protocol) through which browser-based XMPP clients can communicate with the Instant Messaging server.
Instant Messaging 7.2 is an XMPP client/server solution, able to communicate with XMPP-compliant servers, clients, and gateways. Gateways are available in the open-source community to enable communication between Instant Messaging server and AOL, Yahoo, and other instant messaging systems.