Once you associate an email with your Stack Exchange OpenID, you can't change it, this is [meta-tag:status-bydesign].  Says [Kevin Montrose][1]: 

> If you've lost access to the e-mail you registered with initially, create a new openid.stackexchange account and either add it to your Stack Overflow account (via your profile page, if you're still logged in) or create a new Stack Overflow account and email us via the Contact link so we can merge the two accounts.

<sub>From: [How do I change the email address associated with my Stack Exchange OpenID?](http://meta.stackexchange.com/a/102469/144987)</sub>

Rather, you have to create a new SE OpenID here: https://openid.stackexchange.com - confirm via email - then go to your Super User profile, click `My Logins` on the upper right corner, between `flair` and `apps`.  A popup appears - then click `add more logins`.  From there, click the Stack Exchange OpenID option and type your credentials, click `confirm` and you're good to go. 


  [1]: https://meta.stackoverflow.com/users/130213/kevin-montrose