In late December 2017, we announced support for EAI in Q1 2018.
We are happy to announce that EAI is now enabled in Exchange Online and Exchange Online Protection for Office 365. Office 365 users can now send messages to and receive messages from internationalized email addresses.
In addition, we are pleased to announce that EAI is also enabled for outlook.com customers (including hotmail.com, live.com, etc.).
In the meantime, we are working to enable EAI for Exchange Server 2019, the new on-premises version of Exchange that's coming out later this year.