关于Exchange Web Services（EWS）迁移至OAuth 2或弃用OAuth 1的计划咨询

Great question—this is a super common point of confusion when navigating legacy Exchange APIs alongside modern Microsoft authentication tools. Let’s break down the details clearly:

Quick Clarification First #

First, a small correction to avoid mix-ups: EWS does use the OAuth 2.0 protocol for authentication, but it relies on Azure AD’s v1.0 endpoint (https://login.windows.net/common/oauth2/authorize) instead of the v2.0 endpoint you mentioned for Graph. The "version 1" you’re referencing is the Azure AD endpoint version, not the OAuth protocol version itself.

Migration & Deprecation Plans #

• No plans to add v2.0 endpoint support to EWS: Microsoft has explicitly positioned EWS as a legacy API, with their long-term strategy focused entirely on Microsoft Graph as the unified API for all Microsoft 365 services. They won’t be investing resources to update EWS to work with the v2.0 Azure AD endpoint.
• EWS support timeline for Exchange Online: Basic authentication for EWS was fully deprecated in October 2022. OAuth 2.0 (via the v1.0 endpoint) remains supported for now, but Microsoft has announced that starting October 1, 2026, they will no longer provide technical support for EWS in Exchange Online. New feature development for EWS stopped entirely in October 2025.
• Strong recommendation: Migrate to Microsoft Graph: If you’re building new integrations or maintaining existing ones, Microsoft strongly advises shifting to Microsoft Graph. It covers nearly all EWS functionality, supports the v2.0 OAuth endpoint, offers more modern features, and receives ongoing updates and official support.

Why the Split Between EWS and Graph Endpoints? #

The v2.0 Azure AD endpoint was built to support a unified ecosystem of APIs (like Graph) and a broader range of identity types (personal Microsoft accounts, work/school accounts, etc.). EWS, being an older API designed specifically for Exchange, wasn’t retrofitted to work with v2.0—Microsoft chose to prioritize the growth and improvement of Graph instead of updating the legacy EWS infrastructure.

内容的提问来源于stack exchange，提问作者Richard Knowler