I've submitted several Internet-Drafts describing a proposed framework
to use IDNA(bis) for non-domain addresses.
The basic idea is to extract anything from the address that fits the
syntax of a valid domain name "label", i.e. strings that roughly match
the "LDH" syntax for "A-labels" and "U-labels". The extracted strings
are then converted using a conversion very similar to IDNAbis.
The draft for the base is:
http://www.ietf.org/internet-drafts/draft-teint-xidna-base-00.txt
Examples for profiles:
http://www.ietf.org/internet-drafts/draft-teint-xidna-email-00.txt
http://www.ietf.org/internet-drafts/draft-teint-xidna-newsgroup-00.txt
http://www.ietf.org/internet-drafts/draft-teint-xidna-zonefile-00.txt
NT