Comment by mcintyre1994

Since we're sharing email sending mistakes: We wanted to start sending users occasional summary emails about activity on the platform that they might be interested in. We wrote the email generation logic first, and then the plan was to start adding different activity events and dogfooding the emails internally to see how they looked in practice. This would be fine because while we developed only internal users would have activity data, so only we'd get emailed. But there was a bug in the "is this email empty" logic so we once sent every user an email with the subject of something like "Check out your recent activity on X" with a few headings and absolutely no activity content. Oops.