Outlook Keeps Prompting for MFA on Every Launch: Fix

You open Outlook, and it asks you to enter your multi-factor authentication code again even though you just did this yesterday. This repeated MFA prompt interrupts your workflow and wastes time. The root cause is usually a broken or missing authentication token that Outlook needs to remember your sign-in session. This article explains why this happens and provides step-by-step fixes to stop the constant MFA prompts.

Why Outlook Prompts for MFA on Every Launch

Outlook uses authentication tokens issued by Microsoft Entra ID formerly Azure Active Directory. When you sign in with MFA, the server gives your device a token that is valid for a set period usually 14 to 90 days depending on tenant policy. Outlook stores this token in the Windows Credential Manager and in the local Outlook profile.

The repeated MFA prompt occurs because the stored token becomes corrupted, expires prematurely, or is rejected by the server. Common triggers include a recent Windows update that resets credential settings, an Outlook add-in that interferes with the authentication flow, or a tenant policy that requires fresh MFA on every sign-in. The token may also be invalid if you changed your password recently or if your device is not domain-joined and uses modern authentication.

Another less common cause is the “Remember MFA for X days” setting in your organization’s conditional access policy. If that setting is set to zero, the server never issues a persistent token. In that case no client-side fix will work and you must contact your IT administrator.

Steps to Stop Outlook from Prompting for MFA Repeatedly

Follow these fixes in the order listed. Test Outlook after each step by closing and reopening the application.

Fix 1: Clear Stored Credentials in Windows Credential Manager

Corrupted credentials in the Windows Credential Manager are the most common cause of repeated MFA prompts. Outlook does not automatically clear these when a token becomes stale.

1. Open Credential Manager
   Press the Windows key and type Credential Manager. Click the search result to open it.
2. Switch to Windows Credentials
   Click Windows Credentials at the top of the window.
3. Locate MicrosoftOffice16 entries
   Scroll down to the Generic Credentials section. Look for any entry that starts with MicrosoftOffice16 or Microsoft.Office.
4. Remove each entry
   Click the arrow to expand the entry, then click Remove. Confirm the deletion. Repeat for every MicrosoftOffice16 entry you find.
5. Restart Outlook
   Close Outlook and reopen it. You will be prompted to sign in once. Enter your credentials and complete the MFA challenge. Outlook should now remember the token on subsequent launches.

Fix 2: Remove and Recreate the Outlook Profile

A corrupt Outlook profile can prevent the token from persisting across sessions. Creating a new profile forces Outlook to establish a fresh authentication state.

1. Open Mail settings in Control Panel
   Press the Windows key, type Control Panel, and open it. Change the view to Large icons and click Mail Microsoft Outlook.
2. Open Profile management
   Click Show Profiles.
3. Remove the current profile
   Select your current profile name and click Remove. Confirm the deletion.
4. Create a new profile
   Click Add, give the profile a name, and follow the prompts to set up your email account. When asked, choose Yes to set this profile as the default.
5. Launch Outlook
   Open Outlook. Sign in with your credentials and complete the MFA challenge. Check if the prompt returns on the next launch.

Fix 3: Sign Out of Office and Sign Back In

A full sign-out clears the cached token inside Outlook itself. This is faster than creating a new profile and works when the token is merely stale.

1. Open Office Account settings
   In Outlook, click File > Office Account.
2. Sign out
   Under User Information, click Sign Out. Confirm the sign-out when prompted.
3. Close Outlook
   Exit the application completely.
4. Clear credential cache again
   Repeat Fix 1 steps to ensure no residual credentials remain.
5. Sign back in
   Open Outlook. Click Sign In and enter your credentials. Complete the MFA challenge. Outlook should now maintain the token.

Fix 4: Disable Problematic Add-ins

Some third-party add-ins intercept the authentication flow and cause the token to be discarded after each session. COM add-ins are the most common offenders.

1. Open Add-ins settings
   In Outlook, click File > Options > Add-ins.
2. Manage COM Add-ins
   At the bottom of the window, next to Manage, select COM Add-ins from the dropdown and click Go.
3. Disable all non-Microsoft add-ins
   Uncheck every add-in that is not published by Microsoft. Click OK.
4. Restart Outlook
   Close and reopen Outlook. If the MFA prompt stops, re-enable add-ins one at a time until you identify the culprit.

If Outlook Still Prompts for MFA After the Main Fixes

Some scenarios require additional steps beyond the client-side fixes above.

Your Organization Requires MFA on Every Sign-In

Your IT administrator may have configured a conditional access policy that sets “Remember MFA” to zero days. In this case no client-side fix will stop the prompt. Contact your IT help desk and ask them to increase the “Remember MFA” duration to at least 14 days. This setting is located in the Azure portal under Microsoft Entra ID > Security > Conditional Access > Policies.

Outlook Uses Basic Authentication Instead of Modern Authentication

Modern authentication is required for persistent tokens. If your Outlook is configured to use basic authentication, the token system does not work and you will be prompted for credentials every time. To check, hold the Ctrl key and right-click the Outlook icon in the system tray. Click Connection Status. Look for the Authn column. If it shows Clear or Basic, modern authentication is not enabled. Your IT administrator must enable modern authentication for your tenant in the Exchange admin center.

Windows Update Reset Credential Manager Permissions

A Windows update can change the permissions on the Credential Manager folder, preventing Outlook from writing new tokens. Open an elevated Command Prompt and run sfc /scannow to repair system files. After the scan completes, restart your computer and test Outlook again.

Cached Mode vs Online Mode: Impact on MFA Token Persistence

Item	Cached Exchange Mode	Online Mode
Token storage location	Local OST file plus Credential Manager	Credential Manager only
Effect on MFA prompts	Token persists across launches if credentials are clean	Token may be rechecked more frequently depending on server policy
Recommended for persistent token	Yes, because the OST file helps retain session state	No, online mode relies solely on server-side session

You can now stop Outlook from prompting for MFA on every launch by clearing corrupted credentials, recreating your profile, or signing out and back in. If your organization enforces per-session MFA, ask your IT admin to adjust the conditional access policy. For ongoing maintenance, check Credential Manager monthly and remove any stale MicrosoftOffice16 entries before they cause issues.