Keith Moore wrote:
Good point. OTOH, if we defined a special version of nameprep for
local-parts to allow mixed-case, then local-parts of internationalized
email addresses would be subject to case-sensitive comparison.
Are you referring to the encoded or unencoded (original) representation?
ACE encoded representations of variable-case local-parts will always fail
since the encoding sequence will differ for each input. OTOH, if the mail
system extracts the original unencoded sequence as part of delivery then
it can do whatever comparisons it wants.
The upside with mail is that comparison is purely a local issue (in
theory) as opposed to DNS where comparison occurs at every cache in
between the end-points.
Another option is for the i18n mail people (whoever that turns out to be)
to just mandate that i18n local-parts are always lowercase normalized.
Of course, strictly speaking, interpretation of the local-part is up to
the domain, but in practice, case-insensitivity is often taken for
granted by both users and software.
--
Eric A. Hall http://www.ehsco.com/
Internet Core Protocols http://www.oreilly.com/catalog/coreprot/