Outlook Classic Stuck on Loading Profile

Based on the behavior described (classic Outlook stuck on “Loading Profile”, crashes or will not start even in Safe Mode, and issues persisting after profile/OST recreation and reinstall), the next supported steps are:

1. Start Outlook in Safe Mode and disable add-ins
   • From Windows, run: Outlook.exe /safe.
   • If Outlook opens, go to File > Options > Add‑ins.
   • At Manage: COM Add‑ins, select Go, clear all check boxes, and select OK.
   • Close Outlook and start it normally.
   • If Outlook works, re‑enable add‑ins one by one, restarting Outlook each time, until the problematic add‑in is identified.
2. Repair or recreate the Outlook profile
   • A corrupted profile can cause Outlook to hang at “Loading Profile” or fail to open mail folders.
   • Create a new profile from Control Panel > Mail > Show Profiles > Add and add the user’s account there.
   • In the Show Profiles dialog, select Prompt for a profile to be used and start Outlook with the new profile.
   • If Outlook now opens and works, the original profile is corrupted and can be removed after any needed data is backed up. When removing a profile, all offline cached content (.ost) for that profile is deleted, so ensure any needed data is on the server or exported first.
3. Repair Outlook data files if specific folders cannot be opened
   • If Outlook shows errors such as “This set of folders could not be opened” when it does start, run the Inbox Repair Tool (scanpst.exe) against the affected .pst/.ost file as documented in Repair Outlook Data Files (.pst and .ost).
4. Check for known crash condition with ucrtbase.dll (if Outlook closes at startup)
   • If Event Viewer shows Outlook crashing at startup with faulting module ucrtbase.dll on Outlook for Microsoft 365 Version 2407 Build 17830.20138 or higher, clear corrupted rules and recreate the profile:
     1. Close Outlook.
     2. Run Outlook.exe /cleanrules from Run.
     3. Create a new Outlook profile if needed.
     4. If the issue persists, remove any remaining rules in Outlook on the web at the mailbox’s Mail > Rules page.
5. If Outlook is frozen but not crashing
   • Confirm no background process is blocking Outlook (for example, auto‑archive or large send/receive) by checking the status bar at the bottom of the Outlook window when it is responsive.
   • If Outlook is completely frozen and none of the above steps help, follow the guidance in Classic Outlook not responding, stuck at "Processing," stopped working, or freezes to create and switch to a new user profile at the Windows level via Control Panel > Mail > Show Profiles.

If, after these steps, Outlook still cannot complete profile creation for multiple users, collect crash details from Event Viewer (especially for ucrtbase.dll) and proceed with the rules cleanup and profile recreation workaround, as this is a documented cause of startup failures in current Outlook builds.

References:

• Troubleshoot Outlook for Windows issues
• Classic Outlook not responding, stuck at "Processing," stopped working, or freezes
• I can’t start Microsoft Outlook or receive the error “Cannot start Microsoft Outlook. Cannot open the Outlook Window”
• Classic Outlook unexpectedly closes at start up on faulting module ucrtbase.dll