Notes Migrator for Exchange: Unable to select Mailbox store when mailbox enabling (4263809)

When mailbox enabling with Notes Migrator for Exchange, the list of mailbox stores is not populated and the list is blank. Without a valid selection, the next button is also greyed out.

This is a permissions issue where the correct permissions are not granted in Exchange.

The following list of permissions is needed:

1. The logged in user (in Windows) must be an Exchange View Only Administrator as a minimum
2. The user specified in the Exchange configuration section of Notes Migrator must be an Exchange Administrator.
3. The user specified in the Active Directory configuration section of Notes Migrator must be an Exchange View Only Administrator as a minimum.

To troubleshoot:

1. In Powershell, type the get-mailboxdatabase command. This should successfully report a list of all the mailbox databases in the Exchange org.
2. In ADSIEDIT, browse to Configuration, Microsoft Exchange, Admin Groups, Servers, Information Stores and make sure that the mailbox database for this server is visible. (A valid mailbox server must be selected initially)