Hi Dieter,
On Tue, Feb 7, 2012, at 08:56 AM, Dieter Klünter wrote:
Never modify a standard track attribute type, all you can do is to create a subtype of mail. On the other hand, your intention does not comply to RFC-5322 which requires that header fields MUST be composed of printable US-ASCII characters.
Unfortunately I'm not in control of what mail clients users are running. This particular case was Thunderbird, but I assume that Apple Mail is also sending bogus UTF-8 mail attribute values.
Alfie