Comment 21 for bug 265016

Using IDN in email addresses is possible. If someone wants to use them now, one
has to type the mail address e.g.
<email address hidden>.
This will be the envelope and the To: header field.

Using the server internetdomänen.com requires the user to enter
xn--internetdomnen-gib.com in host fields.

Why should we be careful to generate such headers and envelopes automatically
and do what IDNA is about: hiding ACE/puny coded domains from the user.

The changes as outlined in comment #6 won't create non-standard behaviour, not
for now and not for the future.
<email address hidden> is and will stay a valid address, may the
cited draft become a standard or not.

If you don't want to see ACE coded domains in mail headers, you should check a
patch in that makes it impossible for the user to create messages with these
addresses even by hand.