Hi Akhil - make sure you're saving these new preferences and not just refreshing the page! If you're still having trouble, just let me know what your email or username is and I'll be happy to unsubscribe you in the system! We don't meant to hold you hostage!
I having the same problem: I have tried to turn off the email alerts several times and sidereel just checkes the boxes automatically back. Please turn off Sidereel Updates sent to my e-mail account.