Security and privacy are extremely important to us. We do not sell user data or provide advertisements based on email information. You can learn about all the ways we protect and secure data here, as well as request a whitepaper that describes our security architecture in detail.
N1 supports two-factor authentication out of the box for Gmail and Google apps accounts, but not other types of accounts. However, you can still use it with other email accounts that are two-factor authentication enabled. The key is that you'll need to create an "app password" to connect your account to N1.
Here's how to do it for some major email providers.
iCloud
Office365