Hey @Mark369, we do have a spam filter which you can activate via https://webmail.optusnet.com.au/. The email client you're using your Optus net email with will also have their own spam filter. You can flag specific senders so their emails are sent directly to your spam/junk folder. These messages are automatically deleted after a set period of time. If you're receiving suspicious emails requesting for any personal details, you can forward these emails through to email@example.com.
It won't block the sender unless you've flagged the email as such. From my knowledge we don't block senders at a server level it's at the email client level. If you're using Optus Net select the email and click the 'Report Spam' button. This will move the email to your Spam folder and also report the email through to us. The problem is that if you're receiving spam from multiple senders, there's nothing stopping them from using a different email address to send through the same spam content.