How do you change super admin default email?

I made a mistake when I created the email for the first time as the super admin.

I used myname@gmail.com and also all@mydomain.com but now I want to use myname@mydomain.com as the super admin so I can use all@mydomain.com for other things.

How do I do that?

Is that possible to switch?

I do not see the option to change the default email away from all@mydomain.com. :(

Please advise.

I appreciate your help on this.

Thank you.