Once you update(through process builder (or) standard UI) any email address in the user record, salesforce will send a mail to the new email address. Go to the mail and click on the confirmation link provided in that, now the user record will be updated with the new email address.
Once you update(through process builder (or) standard UI) any email address in the user record, salesforce will send a mail to the new email address. Go to the mail and click on the confirmation link provided in that, now the user record will be updated with the new email address.
Thanks
Satya