Umlautdomains dont get converted

[b90g]

Version

6.2.70

Installation method

debian packages

Expected behavior

if i subscribe test@umläute-tester.de to a list the email-adress should be on the list.

Actual behavior

its not possible to subscribe that address with umlaut in domain

Steps to reproduce

any list subscribe someone with an umlaut in the domain

Additional information

when i convert the domain to xn--umlute-tester-dfb.de it works.

i assume if have external data sources the email address will just silently fail.

my wish was that sympa would convert it.