RFC 1137 (rfc1137) - Page 2 of 3
Mapping between full RFC 822 and RFC 822 with restricted encoding
Alternative Format: Original Text Document
RFC 1137 E-Mail Address and Quoted Strings December 1989
Restricted RFC 822
This implies a subset of RFC 822 addressing. The quoted-string
form of local-part need not be supported. Standard UUCP mail
transfer falls into this category. Restricted RFC 822 is
undesirable, but in practice it exists in many places.
When a message is transferred from full RFC 822 to restricted RFC
822, and address forms used in full RFC 822 are involved, message
loss may occur (e.g., it may not be possible to return an error
message). This RFC describes a quoting mechanism which may be
used to map between full RFC 822 and restricted RFC 822, in order
to alleviate this problem.
2. Encoding
The RFC 822 EBNF meta notation is used. Any EBNF definitions taken
from RFC 822 are prefixed by the string "822.".
The following EBNF is specified.
atom-encoded = *( a-char / a-encoded-char )
a-char =
a-encoded-char = "_" ; (space)
/ "#u#" ; (_)
/ "#l#" ;
/ "#r#" ;
/ "#m#" ; (,)
/ "#c#" ; (:)
/ "#b#" ; (\)
/ "#h#" ; (#)
/ "#e#" ; (=)
/ "#s#" ; (/)
/ "#" 3DIGIT "#"
The 822.3DIGIT in EBNF.a-encoded-char must have range 0-127, and is
interpreted in decimal as the corresponding ASCII character. The
choice of special abbreviations (as opposed to decimal encoding)
provided is based on the manner in which this mapping is most
frequently used. There are special encodings for each of the
PrintableString characters not in EBNF.a-char, except ".". Space is
given a single character encoding, due to its (expected) frequency of
use, and backslash as the RFC 822 single quote character.
This mapping is used to transform between the two forms of 822.word:
822.quoted-string (restricted RFC 822) and 822.atom (restricted RFC
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