Is anyone aware if using all lowercase header field names in email
messages is ever known to cause any problems?
this is one problem that I've never observed, and I've written programs
that generated all lower-case field names on many occasions. (IIRC some
MTAs will "canonicalize" the casing, but this didn't bother me).
for a few field names there's no obviously correct casing anyway
(is it "Content-type" or "Content-Type"?)
so my guess is that most UAs that couldn't deal with variant casing have
found these bugs pretty quickly.
Keith
p.s. however I do know of at least one UA (sylpheed) that can't deal
with variant casing on month names in dates. it's just lazy coding.