Yes, you can do a nasty kludge like that, but it would be far better to
review the definition of local-part, and decide on a sensible structure
that carefully excluded the encoded forms.
we have two choices:
1. define a convention for I18N-ed local parts which is compatible with
current syntax and invalidates an infintesimal number of existing local-parts
2. invalidate a huge number of existing user agents by creating a new syntax
for local parts that is incompatible with the old one.
choice #2 loses big time.
Keith