Companies that move to Office 365 have to decide what mobile email client to use. A native client that uses Exchange ActiveSync (EAS) or Outlook? In the past, the best choice was probably something like the iOS mail app. Now, Outlook is the focus of Microsoft’s mobile efforts and it’s where all the new functionality appears. EAS is still valuable, just less so than it was before.
https://www.petri.com/best-mobile-office-365-email-client
