Exchange Hybrid is really a rich coexistence option provided by Microsoft, by leveraging existing native Exchange tools. Exchange Hybrid offers customers with an existing Exchange 2010, 2013, or 2016 environments the capability to integrate directly with their Office 365 subscription. Think of the integration as merely an extension of your environment. The integration components can be enabled when a customer deploys Exchange 2010 (SP3), 2013, or 2016 in their environment. Integration is established by creating an Exchange Federation agreement from the on-premises Exchange Organization to the Office 365 subscription. The benefits of Exchange Hybrid are:
Mail routing through Exchange 2010, 2013, or 2016, leveraging TLS
Mail routing control (mail flow from/to Office 365 or on-premises)
Simplified management from Exchange 2010, 2013, and 2016 Exchange Management Console (EMC)
Maintaining a long-term Exchange mailbox presence on-premises and in Office 365
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