In a multi-tenant hybrid scenario in Microsoft Exchange Server 2019 or Exchange Server 2016, you may need an option to select the correct tenant or the remote routing address (RemoteRoutingAddress) when creating an Office 365 mailbox. Currently, Exchange Admin Center (EAC) doesn't have that option.
To fix this issue, install one of the following updates:
For Exchange Server 2019, install the Cumulative Update 9 for Exchange Server 2019 or a later cumulative update for Exchange Server 2019.
For Exchange Server 2016, install the Cumulative Update 20 for Exchange Server 2016 or a later cumulative update for Exchange Server 2016.
Learn about the terminology that Microsoft uses to describe software updates.