Outlook Mail and Outlook Calendar have been updated to version 17.6309.42262.0 this morning. This update puts it in line with the latest Windows 10 Insider release for PC, which has a similar build string.
Unfortunately, we have not seen any new features but we can say app performance is much smoother when opening new emails.
We'll be comparing updates to see if we can find anything else that is new, but for now you can just grab the update from the Store. This update is likely tied to the expected Windows 10 Mobile Insider update that should arrive this week for a preview. As such, there may be new features and abilities turned on with that build once it happens.
Shout out in comments if you find anything new!