A repeating password prompt — even when the password entered is correct — is usually a saved-credential mismatch, not an actual authentication failure.
Common Symptoms
- Outlook prompts for a password every time it opens
- Entering the correct password doesn’t stop the prompt from reappearing
- “Remember my credentials” checkbox doesn’t seem to save
Possible Causes
- “Remember my credentials” not checked, or Windows Credential Manager not saving properly
- An outdated saved password conflicting with a new one after a recent change
- Outlook cache file (.ost) corruption
- A security policy requiring reauthentication on a schedule
Before You Begin
Confirm this is happening in Outlook specifically, not in every Microsoft app — if Teams and other apps are also repeatedly prompting, the underlying account token issue is broader than just Outlook.
Method 1 — Update saved credentials
Open Credential Manager
Windows search → Credential Manager → Windows Credentials.
Method 2 — Recreate the Outlook profile
Create a new profile
Control Panel → Mail → Show Profiles → Add, create a new profile, and set it as the default.
Sign in fresh
Open Outlook with the new profile and complete setup from scratch.
Method 3 — Rename the local cache file
Close Outlook
Fully exit Outlook (check it’s not still running in Task Manager).
Rename the .ost file
Find the .ost file (usually in %localappdata%MicrosoftOutlook) and rename it — Outlook will rebuild it fresh on next launch.
Renaming the .ost cache file forces Outlook to redownload your mailbox from the server, which can take a while for large mailboxes and requires a stable internet connection throughout.
Frequently Asked Questions
Is this a sign my account has been compromised?
Not typically — a repeated but successful password prompt is almost always a local caching issue. If the prompt fails with the correct password, that’s different and worth checking your account’s sign-in activity.
Conclusion
Clearing saved credentials or rebuilding the local Outlook cache resolves the repeated password prompt in most cases without needing to reset the actual Microsoft 365 account password.
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