Update on nested app authentication and deprecation of Exchange Online legacy tokens

Earlier this year, the Office Platform Team announced that Exchange Online legacy tokens are deprecated and will be turned off. This is part of Microsoft’s Secure Future Initiative (SFI) to give organizations the tools they need in the current threat landscape. We’ll begin turning off legacy tokens in February 2025. Publishers and developers are actively migrating their Outlook add-ins to use Entra ID tokens through nested app authentication (NAA) and Microsoft Graph instead of legacy tokens. 

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