Re: POP3 mailbox names and IMAP userids

Roy,

In practice, POP3 and IMAP accounts (mailboxes and user ids, 
respectively) have two important properties:

	(i) Unlike email addresses, which people type, enter
	into address books, and pass around to each other using
	mechanisms other than mail headers and envelopes, they
	are typically configured once per user (or at most, once
	per client machine).  There are some separate issues
	when these things are accessed through web interfaces
	that simulate MUAs, but those are, well, separate issues.
	
	(ii) The typical user finds out the form in which the
	POP3 or IMAP accessing information (which often involves
	a domain name for the server that doesn't correspond
	obviously to the email address either) by getting a
	message that provides the information.  That message may
	appear in a mail message to a different mailbox, on a
	web page, in a paper letter or two, but the point is
	that the user is given it in exact form.  Mailbox
	providers who pass them out in any form that can be
	misinterpreted, even by the totally clueless, are just
	looking for extra customer service calls... and no one
	sane self-inflicts that damage intentionally.

So, this is a non-problem.   If the enrollment message says 
"configure your mail reader so that the Pop server is 
popmail.gnomon.org.uk and your mailboxID is roy12345&&/%", you 
will put that on the relevant screen and move on.   You may 
wonder where on earth those strings came from (I would), but the 
typical user won't care (and, if they decline to tell, you and I 
will get past worrying about it). If, instead, it specifies one 
or more punycode strings, you will put those in and move on. 
And, if they give you something complex in UTF-8 or some other 
encoding, they had better hope your mail-reader knows how to 
handle it, or the customer support line will start ringing. 
When it does, those mail suppliers who can learn will change 
their minds about the presentation format.

An oversimplification of the design principle here is pretty 
close to "people process strings that use characters, and even 
ones they think represent words; computers process bits".

    john


--On Sunday, 16 February, 2003 15:49 +0000 Roy Badami 
<[email protected]> wrote:

> POP3 mailbox names (the argument to the POP3 USER or APOP
> command) are not local-parts.  They identify a mailbox on the
> POP3 server, but are significant only to the POP3 server.
> (RFC 1939 section 7).
>
> In practice, they often are the same as the local-part of the
> e-mail address with which the mailbox is associated, but this
> is neither required by the standards, nor is it universally
> true.
>
> It is not uncommon, for instance, for the POP3 mailbox name to
> be the entire RFC-822 address, possibly with some other
> character (such as percent) substituted for at-sign,
> presumably to accomodate broken clients that believe that a
> POP3 mailbox name cannot contain an at-sign.
>
> Would it be a reasonable design decision for an IMA-aware POP3
> client to apply ToASCII to mailbox names that contain
> international characters?  This would do the right thing for
> mailbox names that corresponded to local parts (probably the
> most common case?).
>...