That's a standard Optus email by the sounds of it. I assume the details mentioned seem roughly correct?
I agree that Optus is definitely doing the wrong thing by sending out emails with links etc.
It should at a minimum include a personal detail (like Hi there Peter)
But as a general rule you should never click on any email link to try access an account or pay a bill. Read it and then go off and login or call seperately.
But I suspect you know that already . As a tip there's no limit to what you can copy and paste into a google search. I just googled 5 sentances in your email and got this. If its a scam then you'll often get many other links suggesting / confirming the same.