Microsoft on-premises server product that runs Office Online.
Hi @Jon Dixon
Thank you for posting your question in the Q&A forum.
I see that the Q&A Assist response has already shared the common Outlook checks, so you can refer to that answer for the initial troubleshooting steps.
To help narrow this down further, here are a few additional checks that are especially helpful when emails from a larger date range are no longer visible:
1. Check Outlook on the Web
Sign in to Outlook on the Web and see whether the missing emails appear there. If they do, your mailbox data is intact, and the issue is related to how Outlook for Windows is displaying or syncing your mailbox.
2. Review the Online Archive mailbox
For Microsoft 365 work or school accounts, some emails may have been moved to an Online Archive due to retention policies, so they may not appear in the main mailbox. If the emails aren’t visible anywhere, your Microsoft 365 administrator can review whether any retention or archive policies apply to that time period.
3. Contact your IT/admin team for Content Search
If the emails are missing or need to be recovered, your Microsoft 365 administrator can run a Content Search in the Purview Compliance Portal. This allows them to locate and restore emails from your mailbox.
Your IT team can refer to this official Microsoft documentation for step-by-step guidance: Create a search for a case in eDiscovery | Microsoft Learn
Could you check Outlook on the Web to see if the emails are there? That will help us guide you on the best next step.
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