Ok I just downloaded Win 10 to see what the new mail app was. If you click add account, other account pop, imap you can start the setup procedure. Enter your Optus email address and password and hit the sign-in button. On the next screen type in the name you want to call the account and then hit sign-in again. That’s it, worked first time on mine.
Hi michaelp, sorry you are having difficulties with your email client. You can view some information on how to setup common email clients here. However Windows 10 is so new that there aren't any specific guides for it, but you should be able to get an idea of how to do it. If you don't know your current Optus username/password, our tech support team will be more than happy to provide it.
Also keep in mind that we recommend using POP3 protocol for your email client rather than IMAP.
As I have the primary and it works ok..I am really convinced now that the second email account will not work..something with optus..of course they cannot enlighten me..It used to work fine on outlook express on my old WIN XP