You can have your password reset and new one sent to your mobile via text via these instructions here . If that does not work, contact optus and ask them to do it for you.
The instructions in that article are slightly outdated.
I'll need to go in and update that support page. Current instructions below (I've tested it and it does work):
1) Login to Webmail using your existing username and password. If we've sent you a temporary password, you’ll need to use this one
2) Select the, ‘Settings’ tab from the top menu
3) Select, ‘Change Password’
4) Enter your current password, you’ll need to enter your new password twice
The part you extracted from the article does not show the recovery procedure which is what is needed in this instance.
I’ve forgotten my OptusNet username or password
Your primary Broadband username is also your primary OptusNet email address. You can find your username under the service summary on your bill.
If you’ve forgotten your password, you will need to contact us and ask us to send out a new temporary password via SMS or email. Change your password by following the steps above.
Ah right. I should have mentioned that.
You need to contact us to reset your password or to confirm your Optusnet email.
We don't have a password recovery process available via self-serve. It's a security measure we have in place.
Yeah, I meant to say password reset not recovery.
Passwords actually should be unrecoverable if Optus is following common security standards which do not allow actually passwords to be stored but rather only store a one-way hash that represents the password.