You can control which mailboxes are displayed by logging into the Archive Manager website as an Administrator and going to Administration | Logins and find the Login in question.
Under the properties of that Login you can then see the Mailboxes tab which will show all mailboxes that are associated with that Login. Also, here you can see the Groups tab which will show all the groups that this Login is a member of and if any of those groups have permissions to mailboxes then this Login will see those mailboxes as well.
