Because this backup set kind is handled by DS-Client in the same way as a Backup from the Cloud (Microsoft Office 365) backup set, equivalent prerequisites apply.

Before you create an Email messages backup set to back up Microsoft Exchange Server data using EWS, see ““DS-Client Installation: Microsoft Office 365 DS-Client plug-in required”” and “Prerequisites for Backup and Restore of Exchange Data”.

Ensure that (1) applicable prerequisites are met and (2) the Microsoft Office 365 plug-in has been installed with DS-Client.