The administration and maintenance of Microsoft Exchange Server to ensure secure, reliable, and efficient email and collaboration services across an organization.
Every plan which includes Exchange Online, apart from Kiosk/Frontline plans. Refer to the Service Description documents for more info: https://learn.microsoft.com/en-us/office365/servicedescriptions/exchange-online-service-description/exchange-online-service-description#features-available-to-some-plans
Business Basic DOES include support for EWS and impersonation.