Outlook keeps asking for your password: causes and fixes

Start with the simple causes

If the password was recently changed, Outlook and other apps on the computer may still hold the old one. The prompt appears, the person types the new password, and something else immediately retries with the old one. Close Outlook, Teams and other Office apps completely, then open Outlook alone and sign in once. Check whether the person can sign into Outlook on the web with the same password; if that fails too, the account itself has a problem.

Look at the prompt itself. A modern Microsoft sign-in window, with the company branding and a multi-factor step, is normal after a password change or a long period away. A plain grey box asking for a username and password usually points to an old connection method or a misconfigured profile.

Clear saved credentials on Windows

Windows stores Office sign-in details in Credential Manager. Open it from the Control Panel, look under Windows Credentials for entries mentioning Microsoft Office, Outlook or your email address, and remove them. Then reopen Outlook and sign in. This clears out stale tokens that cause the app to keep presenting an old password. Also check Settings, Accounts, then Access work or school. If the computer is connected to the work account incorrectly, or connected twice under different names, sign-in can loop. Removing a duplicate connection and re-adding it cleanly often fixes several apps at once. Restart the computer after making these changes.

If the computer is shared, or someone has signed into Office with a personal Microsoft account as well as the work one, the apps can get confused about which account to use. Open any Office app, check the account shown in the top corner and under File, Account, and sign out of anything that should not be there. Mixing personal and work accounts on one Office installation is a regular cause of loops.

Clear saved credentials on a Mac

On a Mac, Office stores credentials in the Keychain. Open Keychain Access, search for Exchange, Office and your email address, and delete the matching entries. Quit all Office apps before doing this. When Outlook reopens, it asks you to sign in again with the modern window. If the loop continues, remove and re-add the account in Outlook for Mac. Old setups from years ago may be connected using an outdated method that Microsoft has since switched off. Removing the account does not delete email from the server; it just rebuilds the local copy.

Old profiles and legacy connections

Microsoft has retired older sign-in methods for Exchange Online, sometimes called basic authentication, in favour of modern authentication. A computer with an Outlook profile created long ago, or a very old version of Office, may keep trying the old method and failing. Updating Office to a current supported version and creating a new Outlook profile from Control Panel, Mail, usually resolves it. Before deleting an old profile, check whether it contains any local data files with mail that is not on the server, such as old archive files from a previous email provider. Make sure those files are kept and reattached to the new profile so nothing is lost.

Multi-factor and access policies

If your business uses multi-factor sign-in or conditional access, Outlook may prompt because the device does not meet the rules. A policy might require a company-managed computer, a compliant phone or a sign-in from New Zealand. A staff member travelling overseas or using a new personal laptop can trigger repeated prompts that look like password problems but are actually access decisions. The sign-in logs in the admin centre show the exact reason for each failure.

Authenticator app issues also cause loops. A new phone without the authenticator app transferred, notifications disabled, or the phone clock set wrong can all make the second step fail repeatedly. Re-registering the person's authentication method is usually quicker than troubleshooting the old one. Make sure every staff member has a backup method registered, such as a second phone number or a hardware key, so a lost or replaced phone does not lock them out of email for a day.

When it is not just one person

If several staff get password prompts on the same morning, the cause is probably central: a Microsoft service issue, an expired certificate on a hybrid setup, a recent policy change or an Office update. Check the service health page in the admin centre first, and ask what changed recently before working on individual computers. Fixing one machine at a time when the real issue is a policy wastes hours.

Finally, do not ignore a password prompt that appears out of the blue on an account that was working fine. Phishing pages copy the Microsoft sign-in window closely. If the prompt came from a link in an email rather than from Outlook itself, close it and report it rather than typing your password.