Connect Outlook to local Exchange but without syncronizing with Microsoft Cloud

Short answer​

• The new “Outlook for Windows” can’t connect directly to on‑premises Exchange. It only supports Exchange Online/Outlook.com; other accounts are proxied through Microsoft’s cloud, which is why it insists on syncing your mailbox there. There’s no toggle to bypass this, by design. ([support.microsoft.com](]learn.microsoft.com[/url], Outlook 2010 is long out of support (since October 13, 2020) and is unreliable on Windows 11—that “Not implemented” + Outbox jams pattern is common with old profiles/add‑ins and the legacy MAPI stack. You can sometimes band‑aid it, but it won’t be stable. ([learn.microsoft.com](]support.microsoft.com,
  

  What will work without putting mail in Microsoft’s cloud​

  • Use Outlook for Windows (classic), not the new app
  • Install a supported desktop Outlook (Microsoft 365 Apps “Outlook (classic)” or Office 2019/2021). These connect straight to your Exchange Server via MAPI/HTTP—no cloud copy. Microsoft’s support matrix explicitly lists only Exchange Online for the new Outlook; on‑premises Exchange isn’t supported yet.
  • Use a non‑Microsoft client that talks to Exchange directly
  • eM Client (Exchange/EWS) or Thunderbird (EWS via ExQuilla or recent native EWS work) connect to on‑prem Exchange without routing mail through Microsoft’s cloud. ([services.addons.thunderbird.net](]emclient.com
  • , blog.thunderbird.net"]guidingtech.com[/url]
  • Use Outlook on the Web (OWA) from your Exchange Server
  • 100% browser‑based, no cloud copy at Microsoft. (Available on every supported Exchange version.

  If you try to keep Outlook 2010 a bit longer (not recommended)​

  • Recreate the Outlook profile (Control Panel > Mail > Show Profiles > Add) and rename the Send/Receive file (Outlook.srs) to rebuild it—these are the two fixes that most often clear “Not implemented” and Outbox stalls. Also test Outlook in Safe Mode to rule out old COM add‑ins. This can buy time but won’t fix the fundamental compatibility gap on Windows 11. (
    

    Why the new Outlook wants to upload your 24 GB​

    • For non‑Microsoft accounts it uses “Sync your account to the Microsoft Cloud,” which keeps a copy of mail/contacts/calendar in Microsoft’s datacenters to enable features and cross‑device sync. On Windows, this applies at least to Gmail/Yahoo today; the behavior you’re seeing is consistent with that architecture. There’s no per‑account opt‑out on Windows once you add the account in the new app.
      If you want, tell me:
    • Which Exchange version you’re on (2010/2013/2016/2019)?
    • Are you open to installing Outlook (classic) from Microsoft 365 or Office 2021, or would you prefer a third‑party client?
      I’ll give you step‑by‑step setup tailored to that.