Simple Mail Transfer Protocol
This specification has been revised 9 times since RFC 772 (1980). Each document below formally obsoleted the one before it; the versions still in force are listed first.
Revision timeline
Current version — implement against this
Superseded versions — historical reference only
- RFC 772Mail Transfer ProtocolObsoletedSeptember 1980replaced by RFC780
- RFC 780Mail Transfer ProtocolObsoletedMay 1981replaced by RFC788
- RFC 788Simple Mail Transfer ProtocolObsoletedNovember 1981replaced by RFC821
- RFC 821Simple Mail Transfer ProtocolObsoletedAugust 1982internet standardreplaced by RFC2821
- RFC 974Mail routing and the domain systemObsoletedJanuary 1986historicreplaced by RFC2821
- RFC 1425SMTP Service ExtensionsObsoletedFebruary 1993proposed standardreplaced by RFC1651
- RFC 1651SMTP Service ExtensionsObsoletedJuly 1994draft standardreplaced by RFC1869
- RFC 1869SMTP Service ExtensionsObsoletedNovember 1995internet standardreplaced by RFC2821
- RFC 2821Simple Mail Transfer ProtocolObsoletedApril 2001proposed standardreplaced by RFC5321
This lineage is derived automatically from the “obsoletes” relationships recorded in the public RFC Editor index — no editorial judgement is applied to the ordering. The most recent document in the chain is RFC 5321 (October 2008).