Targeting Trouble Spots in New Outlook

New Outlook could disrupt some processes due to missing features, but the feature gap with classic Outlook is closing. The accompanying chart (fig. 1) gives the Mar. 2026 status of some features of classic Outlook that were missing in new Outlook for Windows.

The most immediate problem for many enterprise customers will be COM add-ins and related extension technologies, including .NET add-ins (also called “VSTO” add-ins after the Visual Studio Tools for Office tool set), and Visual Basic for Applications (VBA) macros. Many of these were developed by Microsoft, partners, and some customers to integrate Outlook into other applications. Customers moving to new Outlook will have to do without or replace them with new JavaScript add-ins, some of which are already available for Salesforce and Microsoft customer relationship management (CRM) applications.

Also, customers who host Exchange Server themselves or in third-party services will be able to use new Outlook for Windows when Exchange Server SE CU1 ships, probably in the first quarter of 2026. However new Outlook will only be able to connect via the IMAP protocol, which does not support many Outlook features. These customers will likely keep classic Outlook, unless their e-mail systems are very limited by design, for security or other reasons.