Popular Mail Client will support IDN in a new version
Starting with the version 6.0 The Bat! supports IDN (Internationalized Domain Names)
IDN (Internationalized Domain Names) are the domain names that contain national alphabet characters. The names composed from the characters of the non-latin alphabets, such as Arabic, Chinese, Cyrillic, Greek, etc., as well as the Latin alphabet-based characters with diacritics, such as French, German etc. are related to such domain names. Thus, The Bat! can process any addresses containing national alphabet characters. At the present time The Bat! v6 is at the stage of Alpha testing. You can take part in testing and discussing this version subscribing to the mailing list.