The only password that is created for use only in Thunderbird is the 'Primary Password' - it is created in Thunderbird and used to stop prying eyes seeing stored mail account passwords. This is really only used by people who share access to one computer and also have access to your User Account. So, they have access to see everything in Thunderbird in your profile. Hence, the use of 'Primary Passwords'. * https://support.mozilla.org/en-US/kb/protect-your-thunderbird-passwords-primary-password All other passwords are mail account passwords used to access the server and download mail. Mail account passwords can only be created or modified in the webmail account accessed via a browser. Those mail account passwords are stored here in Thunderbird. If the mail account password is stored in Thunderbird - check via method below - see if it can be used to logon to webmail account. In Thunderbird * Settings > Privacy & Security * Under 'Passwords' section * Click on 'Saved Passwords' * click on 'Show Passwords' * If prompted for a password and you have set up a Primary Password then enter the Primary Password. * Otherwise you may be prompted in a eg: 'Windows Security' pop up window asking for password - when you start up computer and use a password to logon to User Account - that is the password required. If you access your webmail account and change your password then you need to update the stored password in Thunderbird. Using the info above to access the stored passwords: * right click on the relevant 'mailbox' or 'imap' and 'smtp' lines and select 'Edit Password' * Completely clear all contents and then carefully type in the correct/new/updated password. * Click on 'Close' * Then Exit Thunderbird and wait a few moments for background processes to complete / * Start Thunderbird. When loggin on to your webmail account - If stored password does not work, you will find the website should provide a 'forgotten password' link. Follow instrcutions to regain access to webmaila ccount. Reset the password, then you can reset the stored password in Thunderbird. If no password was stored for the mail account, then when prompted for password, type in password, select checkbox to 'Remember Password' and click on 'OK'. It should then get saved. I believe bigpond uses telstra . https://signon.bigpond.com/login