1. Clear the saved password Windows is holding
When a password changes, Windows can keep offering Outlook the old one. Outlook fails, asks you, you type the new one — and Windows quietly hands over the stale copy again next time.
- Close Outlook.
- Open Credential Manager from the Start menu and choose Windows Credentials.
- Remove entries mentioning Outlook, Office, MicrosoftOffice16 or your mail server’s name.
- Reopen Outlook, enter the password once, and tick Remember my credentials.
2. Check “Always prompt for logon credentials” is off
On Exchange accounts in classic Outlook there is a setting that makes Outlook ask every time, by design. Go to File → Account Settings → Account Settings, select the account, choose Change → More Settings → Security, and make sure Always prompt for logon credentials is unticked.
3. Test Autodiscover
Autodiscover is how Outlook finds your mail server’s settings. When it points at the wrong place — an old server, a previous provider, a website host that answers but is not your mail server — Outlook can end up asking a server that does not know you for a password, over and over.
- Hold Ctrl, right-click the Outlook icon in the system tray and choose Test Email AutoConfiguration. Untick the two Guessmart options and run it: the results show where Outlook is being sent.
- Use Microsoft’s free Remote Connectivity Analyzer at testconnectivity.microsoft.com, which tests Autodiscover from outside your network.
- Check your DNS: the
autodiscoverrecord for your domain should point at your current email provider. A leftover record from a previous provider is a classic cause after a migration.
Our answer page What is Autodiscover? explains how it works.
4. Is your Outlook too old for modern sign-in?
Microsoft switched off basic authentication for Outlook connections to Exchange Online in October 2022. Microsoft 365 now expects modern authentication, which very old Outlook versions — Outlook 2010, and 2013 without the right settings — cannot do properly. The symptom is a password prompt that never accepts anything.
The fix is a supported Outlook version. If you are on Microsoft 365, the Outlook included with Microsoft 365 Apps is always current.
5. Multi-factor authentication and app passwords
If multi-factor authentication was switched on recently, Outlook may be trying an old sign-in method. Current Outlook versions show a Microsoft sign-in window that handles the second factor. Older setups sometimes relied on “app passwords”, which may have been revoked — remove the account and add it again so Outlook uses modern sign-in.
6. Rebuild the Outlook profile
If none of the above helps, the profile itself may be damaged. In Control Panel → Mail → Show Profiles, add a new profile, set up the account in it, and set Outlook to use it. On an Exchange account your email lives on the server, so nothing is lost — Outlook simply downloads it again. Remove the old profile once the new one is working.
7. Server-side causes worth ruling out
- An expired or mismatched certificate on the mail server, which produces security warnings and then password prompts.
- The PC’s clock being well out — sign-in tokens are time-sensitive.
- A locked or disabled account, for example after too many failed attempts from an old phone with a saved password.
If you are on the new Outlook for Windows
The new Outlook behaves differently. If it will not connect at all to an Exchange Server or hosted Exchange mailbox and says “We couldn’t reach the email server”, that is not a password problem: the new Outlook does not support on-premises Exchange. Our guide to the new Outlook and Exchange Server explains what to do.