You can set up tpg email in an email client like Mail for apple products, Outlook for Windows or Gmail for android - or use one of the many other email clients to get email.
The email clients still work even when the TPG Post Office is down.
The TPG service status page https://support.tpg.com.au/servicestatus is saying the matter is resolved, however it clearly isn't.
Our Network Team is still looking into this matter as some of our customers are still unable to use Post Office. We'll be in touch again for further updates. Please visit this link, so you can setup your TPG email in the meantime: Setting up email on your iPhone and Android phones. Apologies for the inconvenience.