Enabling Two factor authentication, humane notifications and password resets all need an E-Mail as a basis.
Two Factor Authentication with an E-Mail would require you to follow a link or insert some code or passphrase received via E-Mail after logging in.
Humane Notifications are such, that do not annoy and do not cause stress and mental illness. They do the opposite of what notifications do for commercial applications.
- It prevents FOMO and related such illnesses, instead of causing it.
- Notifications are sent with restraint and only if wished or truly necessary.
- It keeps the user up to date with what they need
Password Resets via E-Mail
This is a well-known feature, the service sends a link via E-Mail, following which will then make a password reset possible.