Multi-factor Authentication requires the user to have some information that only they could have to log into an account.
Two-Factor Authentication (also known as Multi-factor authentication, 2FA, two-step verification, or TFA) is an extra layer of security enforced during authentication that requires not only a password and username but also something that only that user has on them, that is a piece of information only they should know or have immediately at hand such as a physical token, a phone application, or a device.
SendGrid no longer accepts Basic authentication for API calls when two-factor authentication is enabled for a user. You can now only use two-factor authentication if you are authenticating with an API key. For more information, see Authentication.
With SendGrid, you can turn this security feature on in your Account Settings.