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Re: dots in local parts

2003-08-26 02:19:37
On Monday, August 25, 2003, at 11:41 , David W. Tamkin wrote:
I'm not sure in which RFC (or where else) to look this up.  To my
understanding, a period is allowed in the middle of the local part of an email address but it must be between two characters that are letters of the alphabet or digits; it may not be the first character of the local part, nor the last one before the at-sign, nor next to another period or any other
punctuation mark.  Is that correct?

From RFC 2822
3.4.1. Addr-spec specification

   An addr-spec is a specific Internet identifier that contains a
   locally interpreted string followed by the at-sign character ("@",
   ASCII value 64) followed by an Internet domain.  The locally
   interpreted string is either a quoted-string or a dot-atom.  If the
   string can be represented as a dot-atom (that is, it contains no
   characters other than atext characters or "." surrounded by atext

   characters), then the dot-atom form SHOULD be used and the
   quoted-string form SHOULD NOT be used. Comments and folding white
   space SHOULD NOT be used around the "@" in the addr-spec.

addr-spec       =       local-part "@" domain
local-part      =       dot-atom / quoted-string / obs-local-part

and

atext           =       ALPHA / DIGIT / ; Any character except controls,
                        "!" / "#" /     ;  SP, and specials.
                        "$" / "%" /     ;  Used for atoms
                        "&" / "'" /
                        "*" / "+" /
                        "-" / "/" /
                        "=" / "?" /
                        "^" / "_" /
                        "`" / "{" /
                        "|" / "}" /
                        "~"

atom            =       [CFWS] 1*atext [CFWS]

dot-atom        =       [CFWS] dot-atom-text [CFWS]

dot-atom-text   =       1*atext *("." 1*atext)

so, a dot-atom is defined as a dot-atom-text enclosed in CFWS (Comment or Foldable White Space) and dot-atom-text is defined as at least one atext at the beginning and end. As I read this

"$bob.charles!" LEGAL
.bob        NOT LEGAL
bob.        NOT LEGAL
bob!        LEGAL
bob^3       LEGAL

please note that some clueless sysadmins will insist that the first character cannot be a numeric. They are 100% wrong.


--
There's nothing to do, so you just stay in bed [ah, poor thing] Why live in the world when you can live in your head?


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