Re: A couple of comments on the open issues...

At 23:53 03/02/13 +0000, Adam M. Costello wrote:

>Roy Badami <[email protected]> wrote:

> > I'm particular keen that the use of a tag or suffix with a local
> > username in not broken by IMAA.  Many MTAs provide the functionality
> > that all mail addressed to <user><delimiter><suffix> will be delivered
> > to <user>, either by default, or as a configuration option.
> >
> > This effectively allows a user of such an MTA (that has been suitably
> > configureed) to have multiple e-mail addresses without requiring any
> > action on the part of the mail administrator, and allows the user to
> > run scripts that process their mail according to the suffix.
>
>So if IMAA operates on the entire local part, this multiple-address
>feature will be unavailable to users with internationalized local parts.
>This is a good argument in favor of having IMAA operate independently on
>subparts of the local part.

First a question: Is subadressing just something that is done
by a few email systems locally, or is it something specified
in some of the email standards? The use of different separators
in different systems seem to suggest the later. If that's the
case, to what extent do we really have to consider it here?

Also, using subaddressing seems to be quite popular for high-end users.
But is it actually very much used by the bulk of users (the
proverbial hotmail/yahoo/... crowd)? My guess would be that it's not.
If that's the case, then this may give us some slack, because as
far as I understand, the main push for internationalized addresses
is from average users, not necessarily high-end users. It's also
easy to imagine that users have a single internationalized
address (for personal mail) and a bunch of structured addresses
(for list subscriptions,...).

A third thing I have just thought about is that the design of
punycode actually has some very nice properties that allow
separation of the subnet address in most cases even if the whole
LHS is encoded in one go. The first thing here is that the
separators, as long as they are ASCII characters, are still
visible in the encoded version. Secondly, very simple pattern
search allows to find all the addresses belonging to the same
primary address, with one exception: It's difficult to check
whether there are accidental non-ASCII characters smuggled in
before the separator. As an example of the last case, assume
'+' is the separator, 'abc' is the primary address, 'AABBCC'
is it's punycode encoding, and we find an address looking
something like xn--+fghAABBCCDDEE, then we don't know whether
the original address was abc+defgh, or whether it was
abcd+efgh or abcde+fgh, i.e. we don't know whether what's
encoded in DDEE comes before or after the +. But we know
that 'abc' comes before the +, because otherwise it would
be encoded differently. So a seach for something like
   m/^xn--+[\x21-\x7e]*$user.*/
(where $user is the punycode encoding of the username in
initial position) will pretty much identify all the
mail for that user.


Regards,    Martin.