Yes, these are some cases I happen to encounter too.

 

The message I think that we might tell them is :

 

Since some email service providers have supported EAI, some Big-name MTAs and email providers should be also  persuaded to upgrade at least receive and send EAI address while their own system can still keep ASCII email address. Otherwise, the customers of these Big-name MTAs and email providers can not receive EAI message, which blocks the communication with some part of the email world, which may have some negative effect on their business.