E-mail address forced to lower case in user ID?!?

[Rich Wales]

I hope people won't feel I'm beating a dead horse, but I feel one of the
issues in this thread requires a bit more clarification.

Earlier, I wrote:

	RW> As far as I'm aware, very few (if any) modern e-mail
	RW> systems actually care about upper vs. lower case in
	RW> their own local user names.

"Stainless Steel Rat" replied:

	SSR> RFC 822 specifically states that local parts of
	SSR> mailboxes *ARE* case sensitive, with the singular
	SSR> exception of the Postmaster local part.

I don't really think we're in serious disagreement here.

My understanding of RFC 822 is that mail transport systems must preserve
upper/lower case distinctions in the local part (left-hand side) of an
address.  That is, the local part of an address must be kept the way it
was originally written, and other systems may not change the case of any
of the letters in the local part (though they may, if they wish, change
the case of the letters in the domain name or right-hand side).

RFC 822 does not prohibit local mail delivery systems from ignoring case
distinctions in their own local mailbox names.  That is, if a site wants
to treat "fred", "Fred", and "FRED" as the same name, and deliver all
mail addressed to any of these alternatives to a single local user whose
account name is "fred", that doesn't violate RFC 822.  (My impression,
FWIW, is that most modern e-mail systems do this very thing.)

But even if a site's local rule is that upper/lower case distinctions
are irrelevant in its own local mailbox names, that does =not= give the
site's software writers permission to change the case on the local parts
of e-mail addresses intended for =other= sites.  For all I know, some
other site may treat "fred" and "FRED" as completely different, and
accept mail delivered only to one or the other.  Or -- though I can't
imagine any sane sysadmin wanting to do this -- some other site might
have two completely separate accounts named "fred" and "FRED", owned by
two different users.  RFC 822 says I'm not allowed to make any assump-
tions in this regard when dealing with other sites' addresses (except
for "postmaster", which I am entitled to assume is always equivalent to
"POSTMASTER", "Postmaster", "pOsTmAsTeR", etc., etc. ad absurdum).

Back in 1982, when RFC 822 was written, there was a tendency by UNIX
mail software writers to force all e-mail addresses to lower case (since
UNIX account names have traditionally used all lower case) -- while, at
the same time, software for TOPS-10, VAX/VMS, and IBM systems tended to
force addresses to upper case (since that was what those systems used).
People needed to be told =not= to change the case of the local parts of
addresses in order to allow e-mail to be exchanged around the net.

When I said that few, if any, modern e-mail systems actually care about
upper vs. lower case, what I meant was that (as far as I'm aware) most
systems today will in fact ignore upper/lower case issues in their own
local mailbox names, and will deliver local mail the same no matter how
the user name is capitalized.  Despite this, though, software still
shouldn't munge the case of the left-hand side of an e-mail address --
and that's why I recommended that GnuPG should stop doing this.

Rich Wales         richw at webcom.com         http://www.webcom.com/richw/
See http://www.webcom.com/richw/pgp/ for my PGP key and fingerprint info
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