Over the last several years, the Microsoft Dynamics 365 team has been working on the Dynamics 365 App for Outlook, otherwise known as the “Lightweight” App, a component that works with both the Outlook on desktop, Outlook on the web (aka Outlook Web Access), and in Outlook on a mobile device. As of the fall release in 2017 for Dynamics 365 for Customer Engagement (I’ll use the old prior nomenclature of “CRM” going forward), I feel the App is ready for prime-time use. But what about the classic Outlook Client software application that’s been around for as long as we can remember? Does it still work? While Microsoft announced that is was deprecated in late 2017, that decision was reversed in Q1 2018. Most users still have the lingering question: What is the difference between the two? Let’s answer that.