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Regular Expressions for Internet Mail

The information below is for an old version of the document.
Document Type
This is an older version of an Internet-Draft whose latest revision state is "Expired".
Expired & archived
Author Sean Leonard
Last updated 2016-09-22 (Latest revision 2016-03-21)
RFC stream Internet Engineering Task Force (IETF)
Stream WG state (None)
Document shepherd (None)
IESG IESG state Expired (IESG: Dead)
Consensus boilerplate Unknown
Telechat date (None)
Responsible AD Alexey Melnikov
Send notices to (None)

This Internet-Draft is no longer active. A copy of the expired Internet-Draft is available in these formats:


Internet Mail identifiers are used ubiquitously throughout computing systems as building blocks of online identity. Unfortunately, incomplete understandings of the syntaxes of these identifiers has led to interoperability problems and poor user experiences. Many users use specific characters in their addresses that are not properly accepted on various systems. This document prescribes normative regular expression (regex) patterns for all Internet- connected systems to use when validating or parsing Internet Mail identifiers, with special attention to regular expressions that work with popular languages and platforms.


Sean Leonard

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)