Outlook Keeps Asking for Password or MFA? Fixes for Microsoft 365 Users

Repeated Outlook sign-in prompts are a common Microsoft 365 headache. You enter your password, approve MFA, and expect to get back to work, only to see the same prompt again. Sometimes the cause is simple, like stale saved credentials. Other times, it points to a broken Outlook profile, broker cache issue, security policy change, or an old mailbox still attached in Outlook.

If Outlook keeps asking for password, the best approach is to work through the likely causes in a safe order.

Is It a One-Time Prompt or a Real Sign-In Loop?

A normal password prompt usually appears after a password change, a session timeout, or a recent sign-out. You sign in once and Outlook works normally again. A sign-in loop looks different. Outlook keeps asking for credentials or MFA over and over, mail may stop syncing, and the app may show messages like “Need Password” or “Trying to connect.” That usually points to a cache, profile, or Microsoft 365 authentication problem.

Common Reasons Outlook Keeps Asking for Password

Some of the most common causes include:

Expired tokens or broken sign-in cache

Microsoft 365 stores tokens so Outlook does not need a full sign-in every time. If those tokens expire or get corrupted, Outlook may keep prompting even when the password is correct.

Cached credentials in Windows

Windows Credential Manager can hold old Outlook or Microsoft 365 credentials. If those no longer match the account’s current sign-in state, Outlook may keep asking again.

Microsoft.AAD.BrokerPlugin or token broker issues

Modern Microsoft 365 sign-in on Windows also relies on broker components and local token storage. If the Microsoft.AAD.BrokerPlugin or token broker cache is damaged, Outlook can get stuck in a repeated sign-in loop.

Outlook profile problems

A damaged Outlook profile can trigger repeated prompts, especially after account changes, migrations, or Office updates.

An old mailbox is still attached

If Outlook has multiple mailboxes added, an old mailbox with removed access or a changed password can keep triggering prompts in the background. This is easy to miss because the main mailbox may look fine.

MFA, Conditional Access, or device registration changes

If MFA methods changed, Conditional Access rules were updated, or the device registration is no longer right, Outlook may not be able to complete sign-in normally.

Classic Outlook with MAPI disabled

If someone is using classic Outlook against Exchange Online, MAPI must be enabled for that mailbox. If MAPI is disabled, Outlook may fail to connect correctly and can trigger repeated connection or sign-in issues.

Safe Fixes to Try First

Check Microsoft 365 service health

If multiple users are affected at the same time, start there. A Microsoft-side outage can cause repeated prompts across many accounts.

Close Outlook and other Office apps fully

Exit Outlook, Word, Excel, Teams, OneDrive, and other Microsoft apps. Then reopen Outlook. If that does not help, reboot the PC.

Remove stale credentials in Credential Manager

On Windows:

1. Open Control Panel.
2. Open Credential Manager.
3. Select Windows Credentials.
4. Look for entries related to Outlook, Office, MicrosoftOffice, ADAL, or Microsoft 365.
5. Remove the old entries tied to the affected work account.
6. Open Outlook and sign in again.

This often clears old saved passwords or tokens that keep forcing bad sign-ins.

Check Access Work or School

If the account is connected oddly at the Windows level, it can interfere with Microsoft 365 desktop sign-in.

1. Open Settings.
2. Go to Accounts.
3. Open Access work or school.
4. Review the connected work account.
5. If the account connection is stale or no longer valid, disconnect it and reconnect it if appropriate for that user.

This step matters most when the user recently changed organizations, changed security settings, or has registration conflicts on the device.

Check for old mailboxes in Outlook

Review the mailboxes attached to the profile. If an unused shared mailbox, former employee mailbox, or retired account is still there, remove it and test again.

Update Office

Make sure Office and Outlook are fully updated before moving to deeper repair steps.

Clearing Broker Plugin and Token Broker Cache

If the basic fixes do not work, clearing the broker-related cache can break a stubborn loop. This is best handled carefully, especially on business-managed computers.

First, fully close Office apps. An IT-style command prompt can do that quickly:

taskkill /f /im outlook.exe
taskkill /f /im winword.exe
taskkill /f /im excel.exe
taskkill /f /im powerpnt.exe
taskkill /f /im onenote.exe
taskkill /f /im teams.exe
taskkill /f /im onedrive.exe
taskkill /f /im msaccess.exe
taskkill /f /im lync.exe
taskkill /f /im Microsoft.AAD.BrokerPlugin.exe

Then rename the token cache folders so Windows can rebuild them cleanly:

ren "%LOCALAPPDATA%\Packages\Microsoft.AAD.BrokerPlugin_cw5n1h2txyewy" Microsoft.AAD.BrokerPlugin_cw5n1h2txyewy.old
ren "%LOCALAPPDATA%\Packages\Microsoft.Windows.CloudExperienceHost_cw5n1h2txyewy\AC\TokenBroker\Accounts" Accounts.old

Some technicians also clear the local token broker cache:

ren "%LOCALAPPDATA%\Microsoft\TokenBroker" TokenBroker.old

After that, reboot the computer and sign in to Outlook again.

If the folders are missing, inaccessible, or immediately recreate with errors, that is usually a good point to involve IT.

When to Rebuild the Outlook Profile

If Outlook still keeps asking for password after credential cleanup and cache resets, rebuild the Outlook profile. A fresh profile often fixes persistent sign-in loops caused by damaged local Outlook settings.

When IT Should Step In

IT should take over when:

• Multiple users have the problem at once
• The issue started after MFA or Conditional Access changes
• Outlook works on the web but not in the desktop app
• Broker cache cleanup did not help
• Device registration looks wrong under Access work or school
• The mailbox may have MAPI disabled for classic Outlook

Final Thoughts

When Outlook keeps asking for password or MFA, the cause is usually stale credentials, broken token caches, Outlook profile damage, old attached mailboxes, or Microsoft 365 security settings. Working through the issue in the right order can save a lot of time and frustration.

If you need help fixing repeated Outlook sign-in prompts, Illini Tech Services supports Microsoft 365 users across central Illinois. Call 217-854-6260 or email [email protected] to get the issue diagnosed and resolved quickly.