Did you change your password recently by any chance? You'd need to go into the email account settings within Outlook and update it there to
It'd still be worth removing the details of your Optus email account from Outlook and re configuring your email settings. The instructions may differ depending on the device you use to access your emails. We have a handy set up guide on our website that you can find here. Let us know how you go! If any questions come up, feel free to send them through.