We announced at Ignite that we are actively working on bringing dynamic plus aliases to Office 365.
To get around existing usage, the plan is for an opt-in setting. Our ETA is to have this available for all customers by the third quarter of 2020.
I will keep you updated in Uservoice on our progress.Billy Purdue commented
Seems silly Outlook.com has had this for half a decade and Office 365 doesn't have it in Exchange yet.