I am creating a custom component for Lightning for Outlook. I need to read the content of email body. Right now the clients:hasItemContext interface provides only attributes like 'people' and 'subject'. Not sure how to read body.
Winter 17 document of salesforce does not mention but salesforce Spring 17 throws some more info into this Interface
As per the documentation you can create an attribute message body .
<aura:attribute name="messageBody" type="String" />
The messageBody indicates the email message on the current email.
Now I am not sure if this will work with 38.0 version of the API but with spring 17 as per doc it should work hence you may have to download latest Lightning for Outlook version .
I would reach out to salesforce to get more info around dates for GA availability of new Lightning for Outlook version.