"You must specify the PrimaryOnly parameter" error when you try to move a primary mailbox to Exchange Online in a hybrid deployment
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Applies to: Exchange OnlineExchange Server 2016 Enterprise EditionExchange Server 2016 Standard EditionExchange Server 2013 EnterpriseExchange Server 2013 Standard EditionExchange Server 2010 EnterpriseExchange Server 2010 StandardMore
You have a hybrid deployment of on-premises Exchange Server and Exchange Online in Office 365 in which primary mailboxes are located in the on-premises environment and archive mailboxes are located in Exchange Online. When you try to move only a primary mailbox from the on-premises environment to Exchange Online by using the Exchange admin center in Office 365, you receive the following error message.
Error: MigrationPermanentException: You must specify the PrimaryOnly parameter
The Exchange admin center doesn't have the option to move only a primary mailbox. To do this, you must use the New-MoveRequest cmdlet.
To move only a primary mailbox, follow these steps: