If you plan to use your Gmail account with an non-Google app such as Outlook or Thunderbird, there are a number of security settings that need to be addressed. If any of the security setting are not set properly, you will get a fairly generic message of “invalid login password”.
1) check the Google instructions for the mail server settings and record server and port numbers.
2) Sign into your gmail account on the same PC as the mail client that you are setting up
3) If you’ve turned on 2-Step Verification for your account, you might need to enter an App password. However, you can turn it off if you are OK without this extra line of security. If you do use 2-Step, you will need to generate a password for your mail client.
4) Sometimes adding a new client or device will be blocked by a captcha. Unlock it by going to:
5) Older versions of Thunderbird, Outlook and mobile mail apps may not conform to Google security standards. If so, you can change a setting “allow less secure apps” to “Turn On” to permit these mail clients access.
If none of the above works, as usual, double check login and passwords, mail servers and mail server ports to be sure you have the correct information entered. If all looks correct, visit Google’s Gmail troubleshooting page.