Transfer mail accounts from one admin to another.

I have one account as admin for e-mails in two different domains. I want to create a new acount to administer all the e-mail accounts form one of the domains, while the old admin will keep the e-mail accounts from the other domain.

Today admin1 administers e-mail accounts for dom1.no and dom2.no.
I want admin1 in to keep e-mail accounts for dom1.no.
I want admin2 to administer e-mail accounts for dom2.no.