If Copilot is only working against an older mailbox identity, the Outlook account currently connected in new Outlook is likely not linked to the Microsoft 365 subscription identity that has Copilot, or the mailbox was added with a different account identity.
Try this in new Outlook:
- Open View settings or go to File > Account info.
- Select Accounts > Your accounts.
- Choose the account that should have Copilot access and select Manage.
- Select Link Accounts.
The Link Accounts option appears when there is a Microsoft 365 subscription with the same email identity as the third-party mail account.
If the mailbox in new Outlook is using a different identity than the one that has Copilot, remove that account and add it again using the exact alias that has the full Outlook experience. In similar cases, adding the account with the exact @outlook.com alias helps Outlook provision it as Outlook.com/Exchange, which is the connection type associated with newer integrations like Copilot.
If search is only showing limited mail, also check Outlook search scope and sync settings:
- Go to Settings > General > Search.
- Update the search scope as needed.
- If older or missing mail is not appearing, go to Settings > General > Offline.
- Increase Days of email to save, then select Save.
Additional search behavior in new Outlook:
- Online Archives are searched automatically.
- Multi-account search is not supported. To search multiple inboxes, select each account and search in All Folders.
- If the missing results are in Deleted items, go to Settings > General > Search, enable Include deleted items, and save.