This has caused me to nearly miss the daily challenge several days over the last several months. Being on a >800 day streak, I would be very sad to miss a day, due to the reminder e-mails not being sent. I have unchecked and checked the "Daily Challenge notifications" and the "Daily Game notifications" checkmarks on my account, but it doesn't change anything. Is this a known bug? I use an @yahoo.com e-mail address, and the e-mails are NOT in my spam folder either - I simply don't receive the reminder e-mails at all.