As per Relevance of the word restricted, we have this rfc below:
Network Working Group S.
Request for Comments: 1137 University College
Updates: RFC 976 December 1989
Mapping Between Full RFC 822 and RFC 822
Restricted
Status of this
This RFC suggests an electronic mail protocol mapping for
Internet community and UK Academic Community, and requests
and suggestions for improvements. This memo does not specify
Internet standard. Distribution of this memo is unlimited
This document describes a set of address mappings which will
interworking between systems operating RFC 822 protocols in a
manner, and those environments where transfer of RFC 822
restricts the character set which can be used in addresses.
transfer of RFC 822 messages is an important case of
[Crocker82a, Horton86a].
This document specifies a mapping between two protocols.
specification should be used when this mapping is performed on
Internet or in the UK Academic Community. This specification may
modified in the light of implementation experience, but
substantial changes are expected
1.
Some mail networks which use RFC 822 cannot support the
character set required by all aspects of RFC 822. This
describes a symmetrical mapping between full RFC 822 addressing,
a form for use on these networks. Any addresses within the
will not use the full RFC 822 addressing, and so any
encoded according to this standard will always represent
addresses. This document derives from a mapping originally
in RFC 987 [Kille86a], where the domain of application was
restricted. Two terms are now defined
Full RFC 822
This implies full support for transfer to and from any legal
822 address. In particular, the quoted-string form of local-
must be supported (e.g., <"Joe Soap"@foo.bar>).
Kille [Page 1]
RFC 1137 E-Mail Address and Quoted Strings December 1989
Restricted RFC 822
This implies a subset of RFC 822 addressing. The quoted-
form of local-part need not be supported. Standard UUCP
transfer falls into this category. Restricted RFC 822
undesirable, but in practice it exists in many places
When a message is transferred from full RFC 822 to restricted
822, and address forms used in full RFC 822 are involved,
loss may occur (e.g., it may not be possible to return an
message). This RFC describes a quoting mechanism which may
used to map between full RFC 822 and restricted RFC 822, in
to alleviate this problem
2.
The RFC 822 EBNF meta notation is used. Any EBNF definitions
from RFC 822 are prefixed by the string "822.".
The following EBNF is specified
atom-encoded = *( a-char / a-encoded-char )
a-char =
and "."), SPACE
CTL, "_", and "#">
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
interpreted in decimal as the corresponding ASCII character.
choice of special abbreviations (as opposed to decimal encoding
provided is based on the manner in which this mapping is
frequently used. There are special encodings for each of
PrintableString characters not in EBNF.a-char, except ".". Space
given a single character encoding, due to its (expected) frequency
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
Kille [Page 2]
RFC 1137 E-Mail Address and Quoted Strings December 1989
822). To encode (full RFC 822 -> restricted RFC 822), first
any quoting from any 822.quoted-string. Then, all EBNF.a-char
used directly and all other CHAR are encoded as EBNF.a-encoded-char
To decode (restricted RFC 822 -> full RFC 822): if the address can
parsed as EBNF.encoded-atom reverse the previous mapping. If
cannot be so parsed, map the characters directly
3.
This mapping should be used for all addresses, at the MTS or
level. It is applied to the 822.local-part of the addresses.
example
Full RFC 822 Restricted RFC 822
Steve.Kille@cs.ucl.ac.uk <-> Steve.Kille@cs.ucl.ac.
"Steve Kille"@cs.ucl.ac.uk <-> Steve_Kille@cs.ucl.ac.
"argle#~"@blargle <-> argle#h##126#@
[Crocker82a] Crocker, D., "Standard of the Format of ARPA
Text Messages", RFC 822, August 1982.
[Horton86a] Horton, M., "UUCP Mail Interchange Format Standard",
RFC 976, February 1986.
[Kille86a] Kille, S., "Mapping Between X.400 and RFC 822",
UK Academic Community Report (MG.19), RFC 987, June 1986.
Security
Security issues are not discussed in this memo
Author's
Steve
University College
Gower
WC1E 6
Phone: +44-1-380-7294
EMail: S.Kille@Cs.Ucl.AC.
Kille [Page 3]
if you see any problems within the linking, don't worry be happy,
this is version 0.1 of the Relevance System and you gotta expect some crappy subroutines sometimes,
just be content we did not write this in Java, which would have made this "bigger and better" HAHAHHA.
RFC documents can be found at I.E.T.F.
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