Unicode attachment names are transliterated

Our site is multinational, including languages with non latin alphabet [russian, georgian, armenian] and therefore we need use unicode also in attachments names. It does not produce any problem to create and edit content with such attachments in normal Drupal, but posting attachments through mailsave module will end with all foreign letters changed to underscore character (similar as transliterate module). This automatic and unchanged filtration is for us unwanted and can be declared as bug.