RFC 1522 (rfc1522) - Page 1 of 10
MIME (Multipurpose Internet Mail Extensions) Part Two: Message Header Extensions for Non-ASCII Text
Alternative Format: Original Text Document
Network Working Group K. Moore
Request for Comments: 1522 University of Tennessee
Obsoletes: 1342 September 1993
Category: Standards Track
MIME (Multipurpose Internet Mail Extensions) Part Two:
Message Header Extensions for Non-ASCII Text
Status of this Memo
This RFC specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" for the standardization state and status
of this protocol. Distribution of this memo is unlimited.
Abstract
This memo describes an extension to the message format defined in RFC
1521 [1], to allow the representation of character sets other than
ASCII in RFC 822 (STD 11) message headers. The extensions described
were designed to be highly compatible with existing Internet mail
handling software, and to be easily implemented in mail readers that
support RFC 1521.
1. Introduction
RFC 1521 describes a mechanism for denoting textual body parts which
are coded in various character sets, as well as methods for encoding
such body parts as sequences of printable ASCII characters. This
memo describes similar techniques to allow the encoding of non-ASCII
text in various portions of a RFC 822 [2] message header, in a manner
which is unlikely to confuse existing message handling software.
Like the encoding techniques described in RFC 1521, the techniques
outlined here were designed to allow the use of non-ASCII characters
in message headers in a way which is unlikely to be disturbed by the
quirks of existing Internet mail handling programs. In particular,
some mail relaying programs are known to (a) delete some message
header fields while retaining others, (b) rearrange the order of
addresses in To or Cc fields, (c) rearrange the (vertical) order of
header fields, and/or (d) "wrap" message headers at different places
than those in the original message. In addition, some mail reading
programs are known to have difficulty correctly parsing message
headers which, while legal according to RFC 822, make use of
backslash-quoting to "hide" special characters such as "<", ",", or
":", or which exploit other infrequently-used features of that
Moore
