Hi Chris,
Thanks for putting in your request! I can definitely see the value in adding IDN support to SmarterMail; however, I don't believe this feature will make it into SmarterMail 16.0. I'm going to go ahead move this thread from the SmarterMail 16.x BETA category to the standard SmarterMail category so it's not lost when we close down the BETA threads down the road.
Thanks again!