Microsoft have just released the Mail.ReadBasic permission into beta for the Microsoft Graph endpoint https://developer.microsoft.com/en-us/graph/blogs/new-basic-read-access-to-a-users-mailbox/ which is a much needed addition that allows the creation of automation and apps that can just access messages at a more meta information level without having access to the Body or Attachments. Privacy and security are always pressing issues especially around email so this can turn down the privacy concerns while also reduce the security concerns of giving full access to content.
Lets look at one use case for this new permission which is getting the Message Headers from a Message that has arrived in a users Mailbox that you suspect might be spam but you want the header information to do some analysis. Normally if you wanted to build an app to automate this you would have to at least assign Mail.Read which would give full access to all email content in a Mailbox (either delegated or every mailbox in a tenant in the case of Application permissions). This new grant allows us to just to get the Meta information like TO/From and all the first class properties which now includes the InternetMessageHeaders https://docs.microsoft.com/en-us/graph/api/resources/internetmessageheader?view=graph-rest-1.0
All you need to get going with using this is an application registration with just the Mail.ReadBasic permission assigned (for delegate access you would also need access to their underlying Exchange Folder or Mailbox your going to be querying via the normal Exchange DACL mechanisms).
I've put the script up on GitHub here https://github.com/gscales/Powershell-Scripts/blob/master/GetMessageHeaderAndProcess.ps1
An example of this in use say if we are looking at the last 60 minutes of our trace logs for messages that where FilteredAsSpam (meaning the message ended up in the Junk Mail folder in the Mailbox)
A few things that are missing for this at the moment are to be really useful it needs to be an Application permission which I believe is coming. The other thing is you really need to be able to enumerate the Folder Name which this restricted at the moment and the ItemClass should be a first class property as you need it to determine the different types of emails you might be detail with.