Outlook Exchange Delegation two trusted domains

I have two Windows 2003 domains and want to allow a user in domainA to delegate to a user in domainB. In Outlook 2003, it seems to allow you to add the delegate and apply the permissions, but when you try to access the mailbox in domainA from the user in domainB, it says you don’t have permission. If you go back to the user in domainA and look again at the permissions you assigned, they are gone.

These are trusted domains NOT in the same forest.

Is there anyway to accomplish this?