Re: Email Subaddressing

["D. J. Bernstein" <[e-mail]>]

> A syntax for subaddresses in local parts,

Sensible definitions such as

   The ``plus-terminated prefix'' of an address is everything up to and
   not including the first "+" character, or the entire address if it
   does not contain a "+" character.

or

   The ``dash-separated components'' of an address are its maximal
   substrings not containing "-" characters. For example, the
   dash-separated components of "jean-marc-sos-request" are the strings
   "jean", "marc", "sos", and "request".

are fine with me.

Such definitions might be useful in, e.g., an informational document
surveying common address formats and their uses.

> The one and only rule that
> is necessary is that the primary address always identifies the same
> entity regardless of what subaddress is attached.

What does this mean? What is an ``entity''? Why is this rule necessary?

More importantly, that rule is inconsistent with reality. There are
a+b@host and a+c@host addresses that are _not_ the same entity.

> I've been asking for alternatives, but the only
> suggestion so far is that we throw away combinations of agents that
> don't already understand one another.  Not very helpful either to those
> who'd like to change existing agents to be able to understand, nor to
> those who want to write new agents.

On the contrary. Someone who wants to write (e.g.) a UNIX delivery agent
that supports qmail's address hierarchy simply has to use the variables
supplied by qmail-local: LOCAL, USER, EXT, EXT2, EXT3, etc.

---Dan
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