Using Classic Outlook on Windows for personal email, calendar, and contact management
To help identify the cause, could you please confirm whether you can successfully sign in to Telstra Webmail using your new password? Also, when you try to reconnect the account in Outlook, does it repeatedly ask for your credentials, display an incorrect password message, or show a specific error code? Are you trying to update the existing account or add it again after removing it? Finally, do you know whether your BigPond account was originally configured using IMAP or POP?