咨询Outlook插件保存CustomProperties所需权限：文档与实际不符问题

Great question—this is a super common pain point lately with Outlook add-ins, and I’ve seen several devs hit the exact same issue. Let’s break this down clearly:

• This isn’t an Office.js bug, but a recent permission policy adjustment that the official docs haven’t caught up to yet.
  Microsoft has been tightening Outlook add-in API permission boundaries over the past few quarters to align with stricter security standards. While older docs state ReadItem permission is enough to save CustomProperties, the current live behavior enforces ReadWriteItem for the saveAsync call. This actually makes logical sense from a permissions model standpoint: writing or modifying item data (even just custom properties) should require write access, whereas ReadItem is intended solely for read-only operations.

• Why did this start happening suddenly?
  It’s almost certainly a gradual rollout of a permissions enforcement update. Microsoft often phases these changes to minimize disruption, so your add-in might have been operating under the older, more permissive rule until the update reached your tenant or user base.

• What are your next steps?
  Unfortunately, there’s no workaround to use saveAsync with just ReadItem permission anymore. The only reliable fix is to update your manifest to use ReadWriteItem and redeploy. To soften the impact, you could:

  • Roll out the updated add-in in batches to test with a small user group first
  • Add a check in your code using Office.context.requirements.isSetSupported to detect if the current environment enforces the new permission rule, and show a user-friendly message if access is insufficient

• How to verify this is expected behavior?
  Checking the latest internal permission matrices (via Office Dev Center reference materials) confirms that writing CustomProperties now explicitly requires ReadWriteItem—the public documentation is just lagging behind on updating this detail.

内容的提问来源于stack exchange，提问作者Sybic2001