public EmailMessage NativeMessage { get; }

Public ReadOnly Property NativeMessage As EmailMessage
	Get

Property Value

This property lets you examine EWS Managed API version of a mail message object, with its specific properties. Some properties may cause exceptions if they were not loaded from the server (so it depends on which parts of messages were requested for download). To request all the info, MailMessageFull needs to be passed to Ews.DownloadItem(FolderId, int, EwsItemParts), Ews.DownloadItem(ItemId, EwsItemParts) or any other method accepting EwsItemParts parameter.

This behavior is different from MailBeeMessage property which is "everything or nothing". With NativeMessage object, you can have an object which is loaded only in part. This approach is more flexible although harder to use. MailBee provides you with the both options (MailBeeMessage and NativeMessage).

Note
This value is only available for mail message items (but not for appointments, contacts, etc). To get items of other types, use NativeItem property.

Reference