The "U" Encoding for Encoded-Words in Email

Document Type Expired Internet-Draft (individual)
Author John Klensin 
Last updated 2012-05-27 (latest revision 2011-11-24)
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


The "Encoded Word" conventions have been used extensively in email headers and elsewhere to permit the encoding of non-ASCII characters where only ASCII ones are normally permitted. The existing specification defines only two kinds of encoding, one of which cannot be understood easily by people and the other of which has been widely discredited. This document specifies a third encoding that is easily accessible by users and much more closely tied to contemporary practices. The current version of the proposal is intended for possible discussion in the EAI, IRI, and PRECIS WGs to see if it sheds light on other issues being discussed in those WGs. It is not, at this point, proposed for adoption.


John Klensin (

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