It sounds like you aren’t alone in Telstra/Bigpond blocking your email address:
This thread provides some information which may be of interest.
You may need to contact Telstra to see if they can whitelist your email address so that emails can be delivered to bigpond email addresses. If they do, it might solve the problem with Bigpond. However, if your Optus email address has been blacklisted more widely, there might be many other email servers which deny delivery of your emails. You may not know this is occurring.
If your email is on blacklists and was caused by the Optus breach, I would be contacting Optus with this information. I would be requesting a new email address from them and asking that any emails received at your current email address, is forwarded to your new address. Over time it would be wise to discard your existing address.
