Outlook.com/Live.com is one of major email services that has also implemented two step verification, its safetyness is really strong where a typical user who wants to hack an account should answer the security question or enter the mobile devices to get the activation code in order to gain access.
When we talk about secure email, we just talk about protecting it from NSA like organisations. But its much more important to save one's email from hackers. NSA may target anyone only if they are doing something wrong, whereas hackers will try to do harm to an user irrespective of what he/she does. Losing money, losing access to online services and a lot of bad things can happen. Though a good email service should protect the user from NSA like organisation, it should also protect an user from hackers and thats where two factor authorisation is a must.