Summary

This article addresses the problem of Outlook repeatedly prompting for your password or displaying a sign-in dialog that reappears immediately after you enter the correct credentials. These steps cover the most common causes — stale cached credentials, outdated authentication settings, and corrupted Outlook profiles — and most fixes take under five minutes.

Symptoms

• The password box keeps popping up, no matter how many times you enter the correct password.
• Outlook signs you out and asks again minutes after you signed in.
• You are stuck in a sign-in loop and cannot get back to your inbox.

In this guide

• 1. Verify Your Account Is Working
• 2. Clear Cached Credentials in Windows Credential Manager
• 3. Sign Out and Back In Within Outlook
• 4. Enable Modern Authentication (Classic Outlook)
• 5. Remove and Re-Add Your Email Account
• 6. Create a New Outlook Profile
• 7. Clear the Outlook Credential Cache (New Outlook)
• 8. When to Contact IT

Before You Start

• Your Microsoft 365 account must be active and your password must be current. Verify by signing in at https://outlook.office.com — if you can access your email through the web, your account and password are working.
• Microsoft Outlook desktop app — Classic or New Outlook for Windows.

Instructions

1. Verify Your Account Is Working

Before troubleshooting Outlook, confirm that the issue is with the desktop app — not your account itself.

1. Open a web browser and go to https://outlook.office.com.
2. Sign in with your work email address and password.
3. If you can access your email successfully, your account and password are fine — the problem is with the Outlook desktop app's cached credentials. Continue with the steps below.
4. If you cannot sign in on the web, the issue is your account or password — not Outlook. Reset it by following How to Reset Your Microsoft 365 Password When You Are Locked Out. If the reset also fails, ask IT to unlock your account and confirm your password has not expired, and tell them webmail rejects you too — that rules out the desktop app entirely.

2. Clear Cached Credentials in Windows Credential Manager

Windows stores your Microsoft 365 credentials in a built-in vault called Credential Manager. When these saved credentials become stale (after a password change, MFA update, or license change), Outlook keeps using the old ones — causing the sign-in loop.

1. Close Outlook completely. If it is frozen, press Ctrl + Shift + Esc to open Task Manager, select Microsoft Outlook, and click End task.
2. Press the Start key, type Credential Manager, and press Enter.
3. Click Windows Credentials (not Web Credentials).
4. Look for entries that contain any of the following in their name:
   • MicrosoftOffice16
   • outlook.office365.com
   • login.microsoftonline.com
   • mso.msoffice
   • Any entry containing your work email address
5. For each matching entry, click the arrow to expand it, then click Remove. Removing these is safe — they are saved copies of your sign-in, not your password itself, and Windows creates fresh ones the next time you sign in. That is precisely why this fixes the loop: the stale copy is what Outlook keeps failing with.
6. Repeat until all Microsoft Office-related credentials are removed.
7. Reopen Outlook. It will prompt you to sign in once with your current password. Enter it, check Remember my credentials if offered, and click OK.
8. If the prompt does not reappear, the issue is resolved.

3. Sign Out and Back In Within Outlook

If clearing Credential Manager did not work, Outlook may have its own internal credential cache that needs to be reset.

1. Open Outlook.
2. Go to File > Office Account (or Account in some versions).
3. Under your user name and email, click Sign out.
4. Close Outlook completely.
5. Reopen Outlook. It will prompt you to sign in.
6. Enter your email address and password. Complete MFA if prompted — How to Use the Microsoft Authenticator App explains how to approve the sign-in on your phone.
7. Check Remember my credentials or Keep me signed in when offered.
8. Test Outlook for 10–15 minutes to verify the prompt does not return.

4. Enable Modern Authentication (Classic Outlook)

Older authentication methods (Basic Authentication) have been deprecated by Microsoft. If Classic Outlook is configured to use them, sign-in loops are a common result.

⚠ This step edits the Windows Registry

The Registry is where Windows keeps its settings. The change below affects your account only, and does not need admin rights.

What it changes: one setting for Outlook, under your own account. Nothing else on the computer is touched, and other people who use this machine are unaffected.

To undo it: right-click the value you created and choose Delete. If the value already existed and you changed it, set it back to what it was.

Rather not? Skip to step 5. It fixes the same sign-in loop by rebuilding the account connection instead, without going near the Registry.

Blocked? If regedit will not open, or you see "Registry editing has been disabled by your administrator", your workplace has locked it. Skip to step 5 — you do not need this step.

1. Close Outlook completely.
2. Press Win + R, type regedit, and press Enter to open the Registry Editor.
3. Navigate to: HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\Identity
4. Look for a value named EnableADAL. If it exists, verify its value is 1. If it does not exist:
   • Right-click in the right pane and select New > DWORD (32-bit) Value.
   • Name it EnableADAL and set its value to 1.
5. In the same location, look for a value named Version. If it exists, verify its value is 1. If it does not exist, create it the same way and set it to 1.
6. Close the Registry Editor and reopen Outlook.

Note: New Outlook for Windows uses modern authentication by default and does not require this step.

5. Remove and Re-Add Your Email Account

If the credential cache and authentication settings are not the issue, the Outlook profile's account connection itself may be corrupted.

1. Go to File > Account Settings > Account Settings.
2. On the Email tab, select your email account.
3. Click Remove and confirm when prompted.
4. Click New to re-add your account.
5. Enter your email address and follow the automatic configuration prompts. Outlook will detect your Microsoft 365 settings and configure the account.
6. Complete MFA verification if prompted.
7. Outlook will create a new connection to the server and re-sync your mailbox. This may take several minutes depending on your mailbox size and cache settings.

6. Create a New Outlook Profile

If removing and re-adding the account does not work, the Outlook profile itself may be corrupted. Creating a new profile is the most thorough fix.

1. Close Outlook completely.
2. Press Win + R, type control, and press Enter to open Control Panel.
3. Search for Mail and open Mail (Microsoft Outlook).
4. Click Show Profiles.
5. Click Add and give the new profile a name (e.g., FixedProfile).
6. Enter your email address and follow the automatic setup prompts.
7. Once complete, select Always use this profile and choose the new profile from the drop-down.
8. Click OK and open Outlook. It will use the new profile and create a fresh local data file.

7. Clear the Outlook Credential Cache (New Outlook)

New Outlook for Windows stores credentials differently than Classic Outlook because it runs on the Edge WebView2 engine.

1. Close New Outlook completely.
2. Open Microsoft Edge (even if it is not your default browser — New Outlook uses Edge's engine).
3. Click the … menu > Settings > Privacy, search, and services.
4. Under Clear browsing data, click Choose what to clear.
5. Set the time range to All time.
6. Check Cookies and other site data and Cached images and files.
7. Click Clear now.
8. Reopen New Outlook. Sign in when prompted.

8. When to Contact IT

Every cause below is server-side, so the ticket has to show the local fixes are already done. List which of Steps 2–7 you completed, quote the full error text including any AADSTS code, and say whether webmail at https://outlook.office.com signs in cleanly. That points IT at your account's Modern Authentication and token-refresh settings instead of your PC.

Contact your IT helpdesk if:

• The password prompt persists after clearing Credential Manager, signing out/in, and creating a new profile — the issue may be related to your account's authentication configuration on the server (Conditional Access policies, MFA enforcement, or token refresh settings).
• You see error messages mentioning certificate, proxy, or federation — these indicate network or server-side authentication issues that require admin intervention.
• The sign-in prompt appears only when connected to the office network but not on home Wi-Fi (or vice versa) — this suggests a network-level authentication proxy or firewall issue.
• Your account was recently migrated to a new tenant or domain — credential caches from the old configuration may need admin-level cleanup.
• Multiple colleagues are experiencing the same sign-in loop simultaneously — this suggests a server-side configuration change, not a local issue.

Troubleshooting

DANGER

The most common cause of Outlook credential loops is stale cached credentials in Windows Credential Manager (Step 2). After any password change, MFA method change, or license update, clearing Credential Manager should be your first step — it resolves the issue in the majority of cases.

Symptom / Error	Potential Cause	Solution
Password prompt reappears immediately after entering correct password	Stale cached credentials	Clear Credential Manager (Step 2).
Yellow "Need Password" banner at top of Outlook	Expired authentication token	Sign out and back in (Step 3).
Prompt appears only after a recent password change	Old password cached in Credential Manager	Clear Credential Manager (Step 2) and enter new password.
"Windows Security" dialog asking for credentials	Basic Auth fallback or missing Modern Auth	Enable Modern Authentication via registry (Step 4).
Prompt appears on Classic Outlook but not on web or mobile	Local profile or credential cache issue	Create a new Outlook profile (Step 6).
Prompt appears only on New Outlook	Edge WebView2 cached credentials	Clear Edge browsing data (Step 7).
Prompt after MFA method change (new phone, new app)	Cached MFA token is stale	Clear Credential Manager (Step 2) and complete MFA again.
"We couldn't sign you in" error with code AADSTS	Server-side authentication policy	Raise a ticket quoting the full AADSTS code and ask IT to check which Conditional Access or MFA policy is blocking you.
Frequent disconnection and reconnection	Network interruption or proxy issue	Test on a different network with the VPN off. If the prompts stop, ask IT to confirm the VPN or proxy is not intercepting traffic to login.microsoftonline.com.

Related Articles

• How to Change Your Microsoft 365 Password
• How to Transfer MFA to a New Phone (Microsoft 365)
• How to Use the Microsoft Authenticator App
• How to Understand MFA and Prevent Account Lockouts
• How to Set Up Self-Service Password Reset (SSPR)
• How to Fix Outlook Not Responding or Freezing
• Understanding Microsoft 365 Account Security — What Protects You and Why
• Understanding Outlook Versions — Classic vs. New vs. Web

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