[exim] desire for free case

Hi, I have users that would prefer to ignore case in
their email addresses. tiffany would like to be able to
receive email as Tiffany, or tiFfany for that matter.
The section in the documentation about case of local parts
doesn't seem to fit this situation but I could be wrong.
Is it standard to put the possibilities in the aliases file?

What should I do?
Right now, anything that isn't a valid username gets rejected
as it should.

exim4, cyrus21

Bob Van Horn          rvh@???