Thanks for contacting here. For your slow issue and Thunderbird issue, let's isolate to make sure these are not due to Maximum Security. Please check if problems persist after you temporarily disable Maximum Security. We have a support document that explains how to do this: Disabling or enabling your Trend Micro Security software
Don't forget to enable your Maximum Security after the confirmation. After confirming, if the problems are due to Bigpond connectivity, we suggest contacting your Internet Service Provider for help.
Also, thank you for being a subscriber of our premium support service! Premium Service Plan gives you 24x7 priority access to a Trend Micro support specialist. If the problems are due to Maximum Security, you can optionally call the Premium Service hotline directly to speak to someone live, who is also equipped with advanced tools to quickly diagnose and resolve your issues. Please find the premium service phone number in the "Call Premium Support" section in this page.