Outlook keeps asking for your password — break the credential loop for good

You type your password. Outlook accepts it. Three minutes later — the same prompt is back. You type it again. Accepts it again. Three minutes later, back. Welcome to the Outlook credential loop. It's one of the most enduring frustrations in Microsoft 365, and it almost never has anything to do with you actually forgetting your password.

I've been working with Outlook for the better part of a decade. I still hit this loop probably twice a year on my own machine. The fixes are real. They work. You just have to do them in the right order or you'll spin in circles for an afternoon.

This post walks through the eight fixes that actually solve it, roughly in the order to try them — quickest and least invasive first. Work through in sequence. One of them will almost certainly do it.

First, look at which prompt you're seeing

There are actually three different Outlook password prompts, and the right fix depends on which one is showing up:

• A Windows Security dialog with a username and password field — usually a stale credential.
• A modern Microsoft 365 sign-in window that looks like a small web page — usually a token or modern auth issue.
• A plain "Need password" banner at the bottom of Outlook with no popup — usually a connectivity or profile issue.

Mention which one you see if you ever ask IT for help. Speeds up the diagnosis a ton.

This guide is about the classic Outlook desktop client (Outlook 2016, 2019, 2021, and Microsoft 365). The new Outlook for Windows uses different authentication plumbing and rarely shows this loop. If you're on new Outlook and seeing it, jump straight to fix 8.

Fix 1: Clear stale Windows Credential Manager entries

This is the most common cause. Try it first. Always.

When Outlook signs in successfully, Windows caches the credential in Credential Manager. Over time those cached entries can go stale or get corrupted, especially after a password change, an MFA reset, or a tenant migration. Outlook keeps presenting the bad cached credential. The server keeps rejecting it. The loop is born.

Here's how to clear it:

1. Close Outlook completely. Open Task Manager and end any leftover OUTLOOK.EXE processes — there's almost always at least one hiding.
2. Open Control Panel, then User Accounts, then Credential Manager.
3. Click Windows Credentials.
4. Look for any entries beginning with:
   • MicrosoftOffice16_Data:
   • MS.Outlook.
   • OneDrive Cached Credential
   • your email address
   • microsoftonline or outlook.office365.com
5. Click each one and choose Remove. Don't be precious about it.
6. Reopen Outlook. You'll get asked to sign in once, properly. If the loop's gone, you're done.

If the loop comes right back, the credential is being re-cached as bad. Move on.

Fix 2: Force modern authentication via the registry

Outlook needs modern authentication (OAuth 2.0) to talk to Microsoft 365. On older installs, or after some upgrades, Outlook can fall back to Basic Auth, which Microsoft has been progressively turning off since 2022. The result is an endless prompt that "succeeds" against the old endpoint and gets rejected by the new one. Maddening.

Force modern auth on with two registry values:

1. Press Win+R, type regedit, press Enter.
2. Go to HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\Identity.
3. Create or set these DWORD values:
   • EnableADAL = 1
   • DisableADALatopWAMOverride = 1
   • Version = 1
4. Restart Outlook.

If you don't see the Identity key, just create it. The 16.0 matches Office 2016, 2019, 2021, and Microsoft 365. Older versions used 15.0.

This is also the fix for the variant where Outlook prompts you forever and never accepts any password no matter what you type. That's Basic Auth being rejected by the server outright.

Fix 3: Check the multi-factor account state

If your IT department recently turned on MFA, or rotated your MFA method, Outlook may be sitting on a token that no longer satisfies the new policy. Easy fix.

1. Open a browser. Go to office.com.
2. Sign in with the same work account.
3. If you get prompted to set up or re-confirm an authenticator app, do it completely.
4. Once Office.com loads cleanly, restart Outlook.

The act of completing MFA in the browser issues a fresh refresh token tied to your device. Outlook can then use it. Fixes a surprising number of cases where the loop started for no obvious reason.

If you've lost access to your MFA method (your phone died, you swapped to a new one, you wiped the authenticator app trying to fix something else), IT will need to reset MFA for your account before Outlook will sign in cleanly. There's no DIY shortcut around this one.

Fix 4: Rebuild the Outlook profile

If credentials and MFA are clean and the loop persists, the Outlook profile itself is probably corrupted. Sounds scary. Isn't, really — for Microsoft 365 accounts everything lives on the server. Nothing local is at risk except cached settings.

1. Close Outlook.
2. Open Control Panel and switch the view to Large icons. This is one of those things where Settings won't get you there — has to be Control Panel.
3. Click Mail (Microsoft Outlook). (If you don't see Mail, you're looking at Settings instead of Control Panel. Search Start for "Control Panel" specifically.)
4. Click Show Profiles.
5. Click Add, give the new profile a name like Fresh, and click OK.
6. Enter your email and password when prompted; let Outlook discover the rest.
7. Back on the Show Profiles dialog, set Always use this profile to the new one.
8. Open Outlook. It rebuilds the local OST cache from scratch — this can take a while for big mailboxes. My last rebuild on a 28 GB mailbox took about an hour and ten minutes.
9. Once it works, you can delete the old profile from the same dialog.

The old .ost file is left behind on disk. After a week or two, if everything's happy, delete the old .ost from %localappdata%\Microsoft\Outlook to reclaim the space.

Fix 5: Check whether OAuth or Basic Auth is in play

Microsoft turned off Basic Auth for Exchange Online in October 2022. If your tenant has any kind of legacy override, or your account was migrated from a legacy system, you might still be limping along with Basic Auth long after the deadline.

To check:

1. In Outlook, hold Ctrl and right-click the Outlook icon in the system tray.
2. Choose Test E-mail AutoConfiguration.
3. Enter your email and password, untick everything except Use AutoDiscover.
4. Click Test.
5. Look at the Log tab. Search for OAuth and BasicAuth.

If you see Basic Auth being negotiated, your account profile is stale. Rebuild the profile (fix 4) and verify modern auth registry keys are set (fix 2).

This Ctrl+right-click trick, by the way, is one of those secret-handshake Microsoft features that no menu will ever lead you to. Took me three years to learn about it.

Fix 6: Refresh expired tokens via a network change

Even with everything configured right, refresh tokens have a lifetime — typically 90 days in Microsoft 365, sometimes shorter under Conditional Access. Once expired, Outlook needs an interactive sign-in. If the device can't reach the right authentication endpoints (a captive portal Wi-Fi at a coffee shop, a misconfigured proxy at the office, a strict corporate firewall), the silent refresh fails and the prompt loop appears.

Try:

• Connecting to a different network. Mobile hotspot is great for testing because it bypasses the corporate network entirely.
• Disabling any third-party VPN temporarily.
• Restarting your machine and signing in fresh.

If the prompt only appears on the corporate VPN, talk to IT. They may need to allow login.microsoftonline.com and *.office.com through the proxy without TLS inspection. Common gotcha.

Fix 7: Conditional Access policies blocking your device

Lots of Microsoft 365 tenants enforce Conditional Access policies that say things like "the device must be Entra-joined" or "the device must be marked compliant by Intune." If your laptop has fallen out of compliance — for example, the BitLocker recovery key changed, or Defender real-time protection got switched off, or the device hasn't checked in for a while — the silent token refresh is denied with an error that Outlook can't really describe to you. So it falls back to prompting.

To check:

1. Open Settings, then Accounts, then Access work or school.
2. Click your work account, then Info.
3. Scroll down and click Sync under Device sync status.
4. Look at the result. Anything indicating the device is non-compliant or unregistered is your culprit.

If you see a problem here, you'll need IT. Usually it's a quick policy nudge or an Intune sync. End users can't resolve Conditional Access denials directly. Sorry.

Fix 8: Delete cached identity files

Outlook 2016 and newer keep a small store of cached identity tokens at:

%localappdata%\Microsoft\IdentityCache

and

%localappdata%\Microsoft\Office\16.0\Licensing

Corruption in either of those (after a crash, a power loss, or antivirus quarantining a file) causes repeated sign-in prompts.

1. Close Outlook, Teams, OneDrive, and any other Office app.
2. Sign out of Office: open Word, click File, then Account, then Sign out.
3. Delete the IdentityCache folder entirely. Windows will recreate it.
4. Reopen Word, sign back in with your work account, and watch for the small "We're getting things ready" message. Let it finish — don't click around.
5. Open Outlook.

Nuclear-but-safe, this one. Resolves the loop for cases that survived everything else, and it's also the right answer for the new Outlook for Windows when it gets stuck.

When to call IT

If you've worked through all eight fixes and the loop is still happening, the issue is almost certainly server-side and not solvable from your machine. Capture this before raising the ticket — it'll save you another support call:

• Which of the three prompt types you see (Windows Security, modern sign-in window, banner)
• The exact text of any error message
• Whether the issue happens on Wi-Fi only, VPN only, or everywhere
• Whether other Office apps (Word, Teams, OneDrive) sign in cleanly
• The output of Test E-mail AutoConfiguration from fix 5

With that in hand, IT can usually pinpoint a Conditional Access denial, a tenant-level Basic Auth override, or a mailbox stuck in a strange migration state.

Last thought

The Outlook password loop is almost never about your password. In order: clear Credential Manager, force modern auth, complete MFA in the browser, rebuild the profile, verify the auth method, check the network, check Conditional Access, then clear the IdentityCache. Nine times out of ten you're done by step three.

And if you make it to step seven and you're still typing your password in for the fortieth time today, take a walk. It's not you.