I have been asked to look at an email conversion. There are 2 domains A and B. Users in A.com do have Active Directory user accounts in B.com b/c of their phone system. My users in A.com need to have all of their email moved to B.com and then start using B.com as their only domain. I am planning on joining the user workstations to the B.com domain. What would be the best way to migrate the mailboxes from A.com to B.com? I can't use a trust between the 2 as there are naming conflicts. A.com is using Exchange 2003 and B.com is using Exchange 2007.