Today I encountered a strange error when trying to create a new task from an email in the MSDYN365 app for Outlook. On the form I was required to put in the activity status of the task, which I wasn't allowed to, and it gave me a curious error message just saying "yt"
Thanks to the magnificent Scott Durow I found out that this is an error caused by a business rule that comes out of the box with new deployments of MSDYN365 Online. To fix it simply find the business rule on the task entity which is named "enter rule name", and deactivate it.
It comes along with the Project Service Automation solution, so there is no way to delete it for now.
Hopefully we'll see a fix soon.