At community.letsencrypt.org, one of our users signed up using GitHub. They had an old, dead email address on their GitHub account. After signing up with Discourse, they removed the old, dead email address from GitHub. However, it’s still present in Discourse. When they go to their preferences page and try to update to a new email, they get a message saying a confirmation email has been sent. However, they never receive a confirmation email. When I change my own email, I do get the confirmation. Could this be linked to the OAuth setting? What should I do to further debug / fix?