Business-class email is included in the Office 365 Essentials and Office 365 Business Premium plans.
Office 365 Essentials is the entry level version of Office 365. It gives you all the “online” collaboration tools in the web browser plus OneDrive for storage and Skype for Business. This is also the plan to buy if you’ve already purchased the latest version of Office (for desktop & mobile Apps).
Office 365 Business Premium is everything. If you want email and the latest version of Office and all the collaboration tools, then this is the plan for you.