I would go to Cisco . com and login. Then, click on your icon and select Profile. then go to Personal , check your email and see if you can change email right there. if not , you should see link to Help on changing email address guide, which may lead you to this page
https://www.cisco.com/c/en/us/about/help/login-account-help.html#~email-change
Regards, ML
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