Re: Email Subaddressing

[Bart Schaefer <[e-mail]>]

On Jul 31,  7:45pm, D. J. Bernstein wrote:
> Subject: Re: Email Subaddressing
> > If the ability to mix and match MUAs and delivery agents is important,
> 
> In practice the interface is the mailbox. The delivery agent writes the
> message to the mailbox in some standard format, and the MUA reads it.

That's true upon receipt, but you included as a local configuration problem
the case where the MUA needs to supply a return address.  In this case the
delivery agent is presumably going to interpret that address when the reply
comes back, so the interface is the address itself.

What's the mechanism for ensuring that they agree on what such a return
address should look like?