Jacob Palme <jpalme(_at_)dsv(_dot_)su(_dot_)se> writes:
Will case of non-ascii character be preserved by IDNA?
No. Characters (ASCII and non-ASCII) are case-folded into lowercase
by Nameprep, iff the string contain _any_ non-ASCII character.
If I send a message with the following header:
To: Maria <maria(_at_)münchen(_dot_)net>
Then the mail will arrive to all recipients with this header
exacly as when I sent it as shown above, i.e. in lower case.
"münchen" will be translated to IDNA format, and then back
to user-friendly format at receipt again.
Headers cannot contain non-ASCII, so you must use IDNA before putting
the data in the header, but that's a technicality.
münchen.net => xn--mnchen-3ya.net
Thus, you will send:
To: Maria <maria(_at_)xn--mnchen-3ya(_dot_)net>
Which is translated, by the receiver, into:
To: Maria <maria(_at_)münchen(_dot_)net>
If I send a message with the following header:
To: MARIA <MARIA(_at_)MÜNCHEN(_dot_)NET>
Then the mail will arrive to recipients in the following
format:
To: MARIA <MARIA(_at_)MüNCHEN(_dot_)NET>
i.e. The upper case Ü in the original message has through
translation to IDMA format, and back again, been converted
to a lower case ü.
Similar in this case; you invoke IDNA on the IDN and then put the
output in the header.
MÜNCHEN.NET => xn--mnchen-3ya.NET
Thus, you will send:
To: MARIA <MARIA(_at_)xn--mnchen-3ya(_dot_)NET>
Which is translated, by the receiver, into:
To: Maria <maria(_at_)münchen(_dot_)NET>
Regards,
Simon