Internationalized Email Addresses, for example প্রোটন@তৌহিদুর.বাংলা is not supported by Proton Mail. When I type my email address in Proton Mail, it weirdly tells me address is not valid.
Note that popular email service providers such as Gmail supports this.
To Reproduce:
Try to send an email to the email address given above.
I would say that you are seeing things from an English speaking community perspective. IDNs and Internationalized Emails exist for a reason. It's bad to see everything new as a potential security risk.