Cannot remove mailbox database [UnwillingToRemoveMailboxDatabase]
Microsoft Exchange Server 2016 Setup can't continue because it can't remove a user mailbox database from the local server without incurring potential data loss.
Exchange 2016 Setup determines whether all mailbox databases have been removed from the server before the Mailbox server role is removed. However, user mailboxes might still remain on the server.
To resolve this issue, move any mailboxes on the server to another Exchange server or, if the mailboxes and the data contained within them are no longer required, disable the mailboxes. Then run Exchange 2016 Setup again.
For more information about how to identify a mailbox in the database, see Get-Mailbox.
For more information about how to move a mailbox, see Mailbox moves in Exchange 2016.
For more information about how to disable a mailbox, see Disable-Mailbox.
For more information about how to remove a mailbox database, see Manage mailbox databases in Exchange 2016.
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