Subject: [EAI] Use of mailto: with EAI addresses

From: Alexey Melnikov <[email-masked]>
Date: Wed, 05 Aug 2009 10:41:26 +0100

I vaguely remember that there was a decision last year to design a 
separate URI scheme (similar to mailto:) for use with EAI addresses. Is 
this no longer the direction the WG wants to take?

---

From: John C Klensin <[email-masked]>
Date: Wed, 05 Aug 2009 09:31:46 -0400

--On Wednesday, 05 August, 2009 10:41 +0100 Alexey Melnikov
<[email-masked]> wrote:

> I vaguely remember that there was a decision last year to
> design a separate URI scheme (similar to mailto:) for use with
> EAI addresses. Is this no longer the direction the WG wants to
> take?

I think your recollection is correct.  The advantage of that
plan is that it does not result in further clutter in the syntax
and the URL scheme --clutter than has to be supported forever in
mail applications-- because the new form could gradually
disappear as EAI deploys.  Its disadvantage is that it further
isolates the use of alternate addresses and makes them less
attractive.

>> I think this method is easy and enough.
>> 
>> But I have an another idea to add new option for the mailto.
>> 
>>  <mailto:[email-masked]&ALT-ADDRESS=ASC
>>  II@ASCII>

> That would work as well.

Actually, it would require some odd special-casing, which would
not be recognized by systems that don't specifically support
that particular syntax extension and, even then, I'm not sure it
would work.  Normally, that syntax would cause

  To: [email-masked]
  ALT-ADDRESS: ASCII@ASCII

The only exception to ?name-value pairs being treated as headers
in RFC 2368 is the special-case for "body".

Now consider a message being set to two addresses via mailto
URLs and remember the rule against assuming very much about
ordering of headers.  So we have

<mailto:[email-masked]&ALT-ADDRESS=ASCII1@ASCII>
and

<mailto:[email-masked]&ALT-ADDRESS=ASCII2@ASCII>
  
resulting in
  To: <[email-masked]>,
<[email-masked]>
  ALT-ADDRESS: ASCII2@ASCII  
  ALT-ADDRESS: ASCII1@ASCII  

And we are in big trouble.  I've also seen attempts, some of
them successful, at using 
  mailto: [email-masked]?to=[email-masked]

Indeed, 2368 explicitly calls out

  mailto:addr1%2C%20addr2
  mailto:?to=addr1%2C%20addr2   and
   mailto:addr1?to=addr2

as legitimate examples.  Consider the third example with
?ALT-ADDRESS and one gets, potentially,

mailto:addr1?to=addr2?Alt-address=addr2-variant?Alt-address=addr1-variant

and you see where this quickly leads.

My recollection is that the WG briefly considered the use of an
additional header for the alternate address(es) and gave up on
it for reasons related to the above.

    john

---

From: Alexey Melnikov <[email-masked]>
Date: Wed, 05 Aug 2009 22:11:47 +0100

>isolates the use of alternate addresses and makes them less
Ok. I think the WG needs to explicitly decide if it wants to design a 
new URI scheme or extend mailto (and possibly add some restrictions on 
what can be expressed).

>in RFC 2368 is the special-case for "body".
Right.

But mailtobis explicitly advises against using values of header fields, 
unless they are recognized and considered safe. So assuming existing 
implementations ignore unrecognized header fields, this shouldn't happen.

>and you see where this quickly leads.
Oh. Right, we lost binding between ASCII and EAI addresses.