On Fri, Feb 22, 2008 at 01:37:20PM -0500, John C Klensin wrote:
The discussion about whether HT should be included as a
permitted character in email message local-parts has identified
another issue that might benefit from explanation. These things
were discussed as "any escaped ASCII character from %0 to %127"
or "control characters" in the 821/2821 context. Since we got
rid of the control characters, we've started talking about white
space and whether or not HT is valid white space.
But, one way or the other, it isn't white space (in the 2822 and
ABNF sense) either. Any of these characters that are permitted
in address local-parts are just characters. In particular,
821/2821/2821bis make no guarantees that any pair of
"joe jones"@example.com (one SP character)
"joe jones"@example.com (two SP characters)
"joe jones"@example.com (one HT character)
"joe jones"@example.com (one SP character, then one HT
Will reach the same mailbox.
Should we insert a comment in paragraph 2 of section 2.4 (which
discusses case matching or the lack thereof) that points this
out? If so, should we encourage implementations to treat these
sequences as "white space", just as we encourage them to treat
addresses as case-insensitive?
It seems to me that this would probably be useful if we leave HT
out of the valid character list and even more so if we include
Isn't the local part interpretation up to the receiving system? Those
may be the same mailboxes for example.com but not foo.com?
:: Jeff Macdonald | Director of Messaging Technologies
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