Same issue here (I have a Lumia 950 XL). I woke up this morning and my email app wasn't working. The live tile shows two emails I received through the night on my hotmail and my work email. Both hotmail and my work email (which is through an exchange server) will show a blue screen with the outlook icon in the center for about 3 seconds then it will crash to the start screen.
What I have tried:
Powering off and on
Soft reset
Updating phone
Disabling Wifi
Re-enabling wifi
Checking for app updates