Thunderbird won't connect to Gmail: How to fix OAuth2 errors

Si Thunderbird does not connect to Gmail using OAuth2The first step is to identify where the problem lies: when logging in with Google, when receiving messages, or only when sending them. Each situation requires checking different settings, and repeatedly changing passwords doesn't always help.

The old method of accessing "unsafe applications" is no longer a viable solution. Thunderbird allows you to authorize access through Google without using your primary password as your login credentials. To restore functionality, review the incoming and outgoing authentication settings, complete the authorization process, and then test both services separately.

Check OAuth2 on the incoming server and in SMTP

Before modifying the account, update Thunderbird and check that you can access Gmail through its website. If you still can't access it, resolve the Google account issue first.

To review an existing account, open Account settingsSelect Gmail and enter Server configurationWithin the security settings, it establishes OAuth2 as an authentication method.

Next, select the name of that same account and check what outgoing SMTP server assignedEdit that server and also select OAuth2. If you have multiple Gmail accounts, verify the username to prevent one from trying to send using another's settings.

For an account configured with IMAP, these are the connection details you should verify:

Service	Server	Port	connection security	Authentication
IMAP Reception	imap.gmail.com	993	SSL/TLS	OAuth2
SMTP Send	smtp.gmail.com	465	SSL/TLS	OAuth2
Alternative SMTP routing	smtp.gmail.com	587	STARTTLS	OAuth2

Use your full email address as usernameOAuth2 and SSL/TLS serve different purposes: selecting the correct authentication method does not compensate for using the wrong port or encryption type.

This table applies to IMAP. If your account uses POP, do not change the protocol or delete the account as a first attempt at repair, especially if you only have downloaded messages on your computer.

Complete the authorization on the Google page

Save the changes and try to receive email. Thunderbird should start the Google authorization process. Since version 153, the system's default browser is used.In previous versions, the access point appeared within Thunderbird.

1. Select the Google account you want to link.
2. Enter your login details on the Google page if prompted.
3. Complete any additional verification that your account has set up.
4. Review the requested permissions and authorize those necessary to manage the email.
5. The process ends and returns to Thunderbird.

You don't need to create an application password to follow this procedure with OAuth2. You also don't need to disable two-step verification.

If the authorization process doesn't complete, check your browser.

If the page remains blank, continually returns to the beginning, or does not allow you to continue, check that it supports JavaScript and cookies are required to log in to Google.In Thunderbird 153 and later, check these settings in the browser where the authorization opens.

If an extension is blocking that page, try a limited login exception or test with a different default browser. There's no need to indiscriminately allow cookies from all websites.

In older versions that display authorization within Thunderbird, the program's own cookie restrictions may also be involved. Avoid applying instructions from an older version without first checking where your login screen appears.

When to delete old credentials

Do not delete all saved passwords as a mandatory step. First, check OAuth2 on both servers and complete the authorization.

If access continues to fail after migrating from an old configuration, open Settings > Privacy and security > Passwords > Saved passwordsIt locates only the entries from the affected account.

Old credentials may appear associated with imap://imap.gmail.com o smtp://smtp.gmail.comIf they correspond to the previous access that is causing problems, delete only those entries, close Thunderbird and try the connection again.

An entry that begins with oauth://accounts.google.com This corresponds to an authorization token. Its presence indicates a correct configuration. OAuth2 stores a token, even if it doesn't use your main password to connect to email..

What to check if you use Google Workspace

A business or school account may have restrictions that are not related to Thunderbird. The administrator can control access via IMAP and which clients are authorized.

If Google indicates that the application is blocked or that you need authorization from your organization, provide support with the exact message and the Thunderbird version. Changing the password or deleting credentials does not remove an administrative restriction.

In personal Gmail accounts, IMAP remains enabled, and you no longer need to find the old switch to turn it on. In Workspace, check your organization's policy.

Check receipt and shipment separately.

After authorizing access, perform two tests: receive a new message and send another to an account you can access. This allows you to verify if the repair affects both incoming and outgoing traffic.

• You receive, but you cannot send: Double-check the assigned SMTP server, your user, and your authentication.
• Google rejects the authorization: Review the selected account, permissions, and any Workspace restrictions.
• The connection times out: Check servers, ports, and connectivity before assuming the password is incorrect.
• A simultaneous connections error appears: Close other clients that use the same account and try again.

If the problem persists, note the exact message and when it appears. This information will allow you to request help without repeating changes you've already made or unnecessarily deleting account settings.