Traditionally, restricting where and from which device users could access their Mailbox in Office 365 required substantial configuration within Active Directory Federation Services (ADFS), or more recently, relied heavily on registration of compatible devices within Intune.
M365 - Exchange Online Center
ENow Software's Microsoft Exchange Online blog built by Microsoft MVPs for IT/Sys Admins.
The functionality in Exchange Hybrid is now quite mature. It’s been available since the launch of Office 365 (or even before if you include the embryotic support in Live@EDU) and provides the rich co-existence functionality that allows organizations to mix mailboxes on-premises and in the cloud, retaining much of the normal sharing capabilities people rely on for day-to-day collaboration.