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.Jason Pearce commented
The "fun" thing about + addresses and . addresses is attempting to unsubscribe from mass-email services like ExactTarget, Constant Contact, Salesforce, etc.
You cannot just ask them to unsubscribe firstname.lastname@example.org. They must also unsubscribe nearly an unlimited number of + and . email aliases too. E.g.:
Those mass-email companies should support wildcard requests for their global blocklists. Something like: