SMTP (Simple Mail Transfer Protocol) is a standard set of rules that define an email message format, and the message transfer agent (MTA), which stores and forwards email.
SMTP was originally designed for only ASCII text, but MIME and other encoding methods have been added which allow other types of files, such as graphic images, to be attached and sent with email messages. SMTP servers route email messages throughout the Internet to incoming mail servers, such as POP or IMAP, which provide message stores for incoming mail. SMTP servers are also referred to as outgoing mail servers.
The SMTP server at MIT is called outgoing.mit.edu.