[VCARDDAV] Internationalized email addresses in vCard 4.0

[Simon Perreault <[e-mail]>]

Hello,

We need some advice from the EAI working group.

vCard 4.0 is a file format for contact information. It's a textual
format and its character set is always UTF-8. One of the information
items it may contain is email addresses. See here:
http://tools.ietf.org/html/draft-ietf-vcarddav-vcardrev-13#section-6.4.2

Basically to list an email address in a vCard you will have a line
looking like this:

EMAIL:[e-mail]

The ABNF for what comes after the colon is "addr-spec", which is defined
in RFC 5322, section 3.4.1.

Now, addr-spec does not allow full Unicode. An internationalized address
would need to be EAI/IDN-encoded, which implies that a vCard app would
need to decode it to display it to a user.

Questions:
- Is this the right way to do it?
- Should we allow full Unicode, which removes the need for decoding from
the vCard app and adds the need for encoding in the MUA?
- Should both forms be possible, should one form be preferred over the
other, or should only one form be allowed?
- What should the ABNF look like for allowing Unicode characters in
email addresses?
- Would it help us in any way if we were to specify a mailto: URL instead?

Thanks,
Simon
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