Confluence Questions notifications are not being sent

Summary

Confluence Questions notifications aren't being delivered

Description

Currently, if you add yourself as a watcher of all questions and/or specific spaces in Confluence Questions you will not receive notifications about it in your e-mail.

Steps to Reproduce

1. In a Confluence Cloud instance with Confluence Questions installed, add yourself as a watcher of all questions
2. Ask a different user to post a question

Expected Results

You receive an e-mail notification regarding the question that was posted.

Actual Results

You receive no e-mail notifications.

Notes

Currently, no notifications are sent at all, including new answers.

This problem only affects certain instances. The current theory is that it only affects certain users - specifically certain email addresses.

Workaround

Navigate to the Security Configuration settings menu (Confluence home -> Settings -> Security Configuration) as an admin. Change the User email visibility setting to public.