TLDR; It’s available only in Exchange 2019 OnPrem onwards and Microsoft 365
The SMTPUTF8 is likely not supported in the OnPremise version of Exchange 2016 or anything earlier.
There is a parameter for SMTPUTF8Enabled in the Set-ReceiverConnector, but even when it was enabled, it was not advertisted.
Get-ReceiveConnector * | Identity, SMTPUTF8Enabled
The parameter is listed as for internal Microsoft use only, changing the value of the paramter made no difference.
https://docs.microsoft.com/en-us/powershell/module/exchange/set-receiveconnector?view=exchange-ps
The EAI (Email Address Internationalization) featured is only listed in th Exchange 2019.
Re, “Email address internationalization (EAI): Email addresses that contain non-English characters can now be routed and delivered natively.”
https://docs.microsoft.com/en-us/exchange/new-features/new-features?view=exchserver-2019
EAI Announcement for Microsoft 365, and there is an unanswered query for On-Prem Exchange in the comments section
https://techcommunity.microsoft.com/t5/exchange-team-blog/eai-support-announcement/ba-p/607595
This is where they mentioned supporting it on the Exchange Server 2019 onwards
https://techcommunity.microsoft.com/t5/exchange-team-blog/eai-support-announcement-update/ba-p/607714
