First of all, open your web browser and visit this URL:- https://telstra.com.au/login to view the official page of Bigpond webmail login.
In the field of username and enter your username there.
To continue, enter your email password correctly in the given field.
Enter your Business ID.
For Verification Process, Choose the options of "I am not a robot".
Enter the button of login.
Read more here;- http://datarecovo.populr.me/how-do-i-reset-my-bigpond-email-password