Message Header Analyzer mail app.
This is the source for the Message Header Analyzer. Install the app from the store here: https://appsource.microsoft.com/en-us/product/office/WA104005406
Because MHA requires the ReadWriteMailbox permission it can only be installed by the Administrator through the Exchange admin center or by a user as a custom addon. Here are some steps I put together:
In order to get the transport message headers I have to use the EWS makeEwsRequestAsync method, which requires the ReadWriteMailbox permission level. See the article Understanding Outlook add-in permissions for more on this. If I could request fewer permissions I would, since I only ever read the one property, but I have no choice in the matter.
When REST is more widely available, and a few REST specific bugs are fixed, I'll be able to switch to REST and request a lower permission level.
Here is a standalone Message Header Analyzer running the same backend code as the MHA app: https://mha.azurewebsites.net/pages/mha.html
https://mha.azurewebsites.net/Pages/test
For both IOS and Android click open an email, then press the three dots under the date. There you should see the MHA icon. See outlook-mobile-addins page for more details.
npm install
npm run build
npm run watch
npm run dev-server
npm run test
npm run test
again.npm run dev-server
npm start
npm clean