Update user email

Updates a user's <code>email</code>. <br/><br/>Use this endpoint with <a href="https://support.iterable.com/hc/articles/9216719179796">email-based projects.</a> To update an <code>email</code> in a userID-based or hybrid project, use <a href="#users_updateUser"><code>POST /api/users/update</code></a>. <br/><br/>In the request body, specify <code>currentEmail</code> or <code>currentUserId</code>, but not both. If you include both, <code>currentEmail</code> takes precedence.<br/><br/>Returns an error if the new email already exists in Iterable, or if the new email has been forgotten via a GDPR request.<br/><br/>Learn about <a href="https://support.iterable.com/hc/articles/29156459027348">identifying users by <code>userId</code> and <code>email</code></a>.