I. As a customer,
You can change your email address in your MyAccount settings:
MyAccount -> Personal Details
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II. As a Seller,
You can change your email address in two places from your seller dashboard- Business Settings and User Account .
Business Settings Email
Go to "Setup Your Store" -> Store Management -> Business Settings -> Then, click on your registered shop link -> Update the email address on the General Tab
User Account Settings Email
In the top right corner of the dashboard, click on the user icon
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Then, Click Edit Profile , and update your email address