See below for some of the Ignite 2017 Exchange sessions that worth watching !
Running Exchange hybrid over the long term
Scott Schnoll’s Exchange tips and tricks
Exchange Online Multi-Geo Capabilities
Modern authentication for Exchange Server on-premises
Troubleshooting Exchange ActiveSync devices
Design your Exchange infrastructure right (or consider moving to Office 365)
The epic Exchange preferred architecture debate
Deploying and using Outlook mobile in the Enterprise
Exchange High Availability and Storage for Insiders
Ten critical areas for those moving from Exchange on-premises to Office 365
Investigate tools and techniques for Exchange performance troubleshooting
Troubleshooting Office 365 identity: How modern authentication works and what to do when it doesn't
Improvements and innovations in calendaring with Microsoft Outlook and Exchange
Thrive as an enterprise organization in Microsoft Exchange Online