How to Fix Thunderbird “Unable to Log In at Server” After a Password Change

Changing your email password should be a simple security step, but in Thunderbird it often triggers a frustrating message: “Unable to log in at server. Probably wrong configuration, username or password.” Your new password is correct, you can log in on webmail, yet Thunderbird keeps refusing to connect.

This error almost never means your account is broken. It usually means Thunderbird is still trying an old saved password, an old authentication method, or an outdated server setting. The fixes below work through the causes in the order that solves the problem fastest.

Quick Answer

To fix the Thunderbird “unable to log in at server” error after a password change, first remove the old saved password in Settings, Privacy, Passwords, then restart Thunderbird and enter the new password when prompted. If it still fails, check that your username is your full email address and that the server uses OAuth2 or Normal Password authentication as required by your provider. For Gmail and Microsoft accounts, you usually must use OAuth2 and sign in through the browser pop-up.

Why This Error Appears After a Password Change

Thunderbird stores passwords separately from your account settings. When you change your password with your email provider, Thunderbird does not automatically know. It keeps sending the old password until you clear it.

There are three other common triggers. First, many providers now block basic password login and require OAuth2, a secure sign-in window from Google or Microsoft. Second, if you enabled two-step verification, some providers need you to re-authorise Thunderbird completely. Third, a small typo in the username, such as missing the “@domain.com” part, will fail only after a change because you rarely retype it otherwise.

Before you start, confirm these basics

• You can sign in to the same account in webmail with the new password.
• Your keyboard layout and Caps Lock are correct.
• Your internet connection is working and the date and time on your computer are automatic and correct.
• You are not connected to a VPN that your provider blocks, if possible test once with it off.

Step 1: Remove the Old Saved Password

This is the fix that works for most people.

1. Open Thunderbird and click the menu button, then Settings.
2. Go to Privacy on the left, then scroll to the Passwords section.
3. Click Saved Passwords.
4. In the list, find every entry for the affected account. There are often two: one for incoming mail (imap:// or pop://) and one for outgoing mail (smtp://).
5. Select those entries and click Remove.
6. Close Settings completely and restart Thunderbird.
7. When Thunderbird asks for a password, type the new password carefully and tick “Use Password Manager to remember this password” if you want it saved.

If Thunderbird never asks for a new password after restart, click Get Messages. That forces a fresh connection attempt and should trigger the prompt.

Step 2: Check Username and Server Settings

If removing the password did not help, verify the account details.

1. Go to Settings, Account Settings, then select your account name.
2. Under Server Settings, confirm the User Name field shows your full email address, for example name@example.com, not just “name”.
3. Confirm the server name matches your provider exactly, such as imap.gmail.com for Gmail or outlook.office365.com for Microsoft 365.
4. Check the port: 993 is standard for IMAP over SSL, and 995 is standard for POP3 over SSL.
5. Set Connection security to SSL/TLS.

Then check the outgoing server. In Account Settings, select Outgoing Server (SMTP) at the bottom of the left list, choose your server, and click Edit. The username there must also be the full address, and it often gets missed because incoming mail may work while sending fails.

You can compare your settings with the details in the Mozilla Support guide to using Thunderbird with Gmail, which lists the correct Gmail server names and authentication choices. Microsoft account users should also review the official Outlook.com POP, IMAP and SMTP settings from Microsoft before changing ports manually.

Step 3: Switch to OAuth2 Where Required

Gmail, Yahoo, and Microsoft mail now prefer or require OAuth2. With OAuth2 you do not type your password into Thunderbird directly. Instead a provider sign-in window opens and you approve access.

1. In Account Settings, Server Settings, change Authentication method to OAuth2.
2. Do the same for the outgoing SMTP server.
3. Remove the saved passwords again using Step 1, because old entries can block the OAuth2 prompt.
4. Restart Thunderbird.
5. When the Google or Microsoft sign-in window appears, sign in with the new password and approve Thunderbird.
6. Allow cookies for the provider domain if Thunderbird asks, because the sign-in window needs them to complete.

If the sign-in window never appears, go to Settings, Privacy, and make sure “Accept cookies from sites” is allowed at least temporarily during setup. You can tighten it again after the account connects.

Account setup in general is covered in more depth in our guide on how to set up an email account in Thunderbird step by step, which is helpful if you decide to remove and re-add the account as a last resort.

Step 4: Handle App Passwords and Two-Step Verification

Some providers still use app passwords for mail apps when two-step verification is on, although the major providers have mostly moved to OAuth2. If your provider dashboard offers “app passwords,” create a fresh one after your password change, because the old app password may have been revoked automatically.

Use that app password in Thunderbird instead of your normal account password, and give it a clear name like “Thunderbird – laptop” so you can revoke it later without confusion. Never reuse an app password across two different apps.

Step 5: Test Antivirus, Firewall, and a Fresh Profile Check

If the settings are correct and login still fails, security software may be scanning encrypted mail and breaking the connection. Temporarily disable the email-scanning feature only, not your whole antivirus, and try Get Messages once. If that fixes it, add Thunderbird as an allowed app in your firewall and keep mail scanning settings at the provider-recommended level.

As a final check, you can start Thunderbird and create a temporary new profile to test the same account. If the new profile connects, your original profile may have a corrupted password file or extension conflict. In most cases you will not need this step, but it is a useful way to prove whether the problem is the account or the profile.

Common Mistakes to Avoid

• Typing the new password over the old prompt without clearing saved passwords: Thunderbird may keep multiple entries, and the wrong one can be used again on the next start.
• Removing only the incoming password: The SMTP entry stays wrong, so receiving works but sending fails with the same error.
• Using just your name as the username: Most modern servers require the full email address.
• Deleting the whole account first: This is rarely needed and risks losing local folders if you have POP mail. Try password and authentication fixes first.
• Ignoring the OAuth2 pop-up blocker: If you close the sign-in window once, Thunderbird may keep failing silently until you restart it and allow the window.

Conclusion

The “unable to log in at server” error after a password change is almost always a local Thunderbird issue, not a lost account. Clear the old saved passwords for both incoming and outgoing servers, confirm your username is your full email address, and switch Gmail and Microsoft accounts to OAuth2 so you sign in through the official window. Test step by step, restarting Thunderbird after each major change, and you will normally be back to sending and receiving mail within ten minutes without deleting your account or losing any messages.

Frequently Asked Questions

Why does webmail work but Thunderbird does not with the same password?

Webmail uses your new password directly on the provider website. Thunderbird uses its own saved copy, which may still be the old password. It may also be using an authentication method your provider no longer accepts, such as basic password login instead of OAuth2.

Do I need to delete and re-add my Thunderbird account?

Almost never. Deleting should be the last resort. Removing saved passwords, fixing the username, and changing authentication to OAuth2 solve the vast majority of cases while keeping your folders, filters, and history exactly as they are.

Where does Thunderbird store my passwords?

Passwords are stored in Thunderbird’s built-in Password Manager under Settings, Privacy, Passwords, Saved Passwords. You can view the sites and usernames there and remove individual entries without affecting your messages.

What if I use POP instead of IMAP?

The same fixes apply. Remove both the POP and SMTP saved passwords, confirm the full email address as username, use port 995 with SSL/TLS for POP, and follow your provider’s current authentication requirement.

The OAuth2 window keeps looping. What should I do?

Clear the saved passwords again, restart Thunderbird, allow cookies in Privacy settings, and make sure your system time is set automatically. Incorrect time can cause secure sign-in tokens to be rejected and the window to repeat.