IMAIL is a program for reading electronic mail. It uses the Internet Message Access Protocol (IMAP, RFC 2060) to access mail that is stored on a server, from which IMAIL fetches individual messages on demand. The server may have many different folders in which messages are stored, arranged in a hierarchical structure like that of a file system. Messages are easily moved or copied from one folder to another.
IMAP also supports the Multipurpose Internet Mail Extensions (MIME, RFC 2045), which facilitate the sending and receiving of attachments. The IMAP protocol supports this by allowing you to fetch some parts of a mail message while leaving others on the server. So, for example, if you receive a message containing a large attachment, it is possible to view the text of the message without waiting for the attachment to be fetched from the server; the attachment is fetched only if you want to view or save it. If you aren't interested in the attachment, you can delete the message without ever fetching it from the server.
In addition to these features, IMAIL provides a user interface very similar to that of the Emacs Rmail mail reader (see Rmail). IMAIL supports most of the same commands and has most of the same key bindings as Rmail. IMAIL is primarily intended to be an Rmail replacement for people who wish to read their mail using an IMAP server. IMAIL can also read and write Rmail files and unix mail (mbox) files, and provides the ability to copy messages from such a file to an IMAP folder, or vice versa; this greatly simplifies the transition from Rmail to IMAIL for those of us who have large amounts of mail stored in files.