[imp] Question about virtual mail with imp

[Tim Grooms]

Set up a new server this past weekend and decided to make the move
from Squirrelmail to Horde/Imp.
In my old set up I had 2 domains configured using sendmail/dovecot to
work with Squirrelmail.

domain.com
domain.us

I set up seperate user accounts for the .us users such as usernameus
to distinguish between
those using .com and .us.  In Squirrelmail, to access the us accounts
the users logged in as
usernameus and had access to their domain.us mail.  I have tried this
same set up with Imp.  I can
log in with the accountus but when I send email out it always uses the
.com extension on
the From/Reply to address even though they are set in the
configuration to username at domain.us
for email account and reply to address.  What do I have to do to make
this type of set up work?

Tim