Problem that copilot is unable to see all my emails in outlook

For anything that requires complete results, keep using Outlook Search as the source of truth. Copilot may summarize or retrieve a subset of relevant messages, but your test shows it is not behaving like an exhaustive mailbox search. To make the issue easier for Microsoft to diagnose, create a small reproducible query: one exact sender, one exact subject phrase, and a known date range where Outlook returns a fixed count. Then ask Copilot the same narrow question and record how many messages it finds. Include screenshots from Outlook on the web, Outlook desktop, and Copilot using the same account. Since the same subset appears in Copilot web and the Windows app, this is more likely a Copilot retrieval/indexing issue than a rebuilt-PC problem.