You may be prompted for the master password. Click the Security button, and go to the Passwords tab.On a Mac, click on the Thunderbird menu and select Preferences…) (On a PC, go to Tools, then Options and then click the Passwords tab. Click Finish to close the window and then click Close to close the Account Settings window.and if you’re successful, you will see a confirmation. Carefully re-enter your password, check the box to Save this password in your password list and then click OK to run the test again. If the password was incorrect, a new window will appear. Select the Outgoing Server tab and ensure that My outgoing server (SMTP) requires authentication is checked, as well as Use same settings as my incoming mail server.Near the bottom right, click More Settings….Click Change and enter your new password in the Password field.