Exchange 2003 for the NT domain users, help!

The NT domain is having their mail removed from it (Exchange 5.5) and the responsibility for the mail is going to a new staff, running a brand new 2003 domain with 2003 Enterprise Server. All the users were recreated, their mail contents were moved over with ExMerge, the security and permissions attributes were changed per Microsft's pages so that an External NT user may use the W2K3 mail account, trusts are in place.

That works fine. That is, the mailbox.

What does not work is this. If the users want to share/delegate their calendar with another user, the other user cannot see them. Same with shared folders, the users cannot get into them unless the permissions are left at Anonymous or Default.

The Exchange login list shows that the users are connected with their NT logon. To share a calendar the only option is to chose a name from the 2003 GAL.

Any ideas how I can get the NT users to be able to manage any shared folders that they create? Any ideas how to get the users to be able to add the mailboxes or calendars of others with whom they have given permission?

The first domain mentioned will stay NT, I already thought of putting in a 2000 server there, but cannot.