Great, happy to read that it’s solved thanks to the community (the best there is!).
For future reference I will mention a few things here that might be scattered around release notes, forum threads, troubleshooting wiki, and other announcements:
- The old SMS app (also called Messaging) which has the green chat icon with a white smiley, was deprecated mid-2016. Since then, the Google Messenger app - with a blue/purple rounded icon - was shipped (and was default on new installations) but both were present until now.
- With Android 6, the old SMS app is not provided anymore, but the SMS are still there and accessible by any SMS app. The Google Messenger app is installed on the phone by default but you can still install another app.
- The version 17.04.3 is missing the AOSP e-mail app - the yellow envelope - but it is part of 17.04.8 once more (update again!). The accounts have to be re-registered though. The Gmail app should be able to handle Exchange accounts anyway.