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.