[horde] horde asks login information twice ?

[Mehmet Fatih Akbulut]

hi all,
i redirected horde's first login to imp.
but when i try to login, it first asks for horde user and password. let's
say its root and akbulut.
when it redirects to imp and again asks for the mail user and password which
is root at akbulut.com akbulut.
couldnt find where to change just login to imp with mail user and password ?
help please ;)
by the way, default domain is akbulut.com so i'd like to be able to login
just with root [not root at akbulut.com] so please help me to achieve this as
well.
many thans in advance.

Cheers,
MFA