Internet e-mail message format

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File Format
Name Internet e-mail message format
Extension(s) .eml
MIME Type(s) message/rfc822
LoCFDD fdd000393, fdd000388
PRONOM fmt/278
Released 1977

Electronic mail (e-mail or email) has been in use on the Internet (and its predecessor, the Arpanet) since the 1970s. A series of RFC documents has specified its standard transmission format. The best-known (and the one which lent its name to the official MIME type for a single message of this format) is RFC 822, but this superseded the earlier RFC 733 and was in turn later superseded by RFC 2822 and RFC 5322.

Collections of multiple messages of this type, such as mailboxes stored for the use of mail programs or list digests and archives, are stored in a number of formats including mbox.


  • MIME type (Internet media type): message/rfc822
  • The extension .eml is sometimes used for files containing individual messages in this format, but this is not universal; other extensions, or no extension at all, can also be used.

Sample files


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