#6 Sendmail fails with senders having special characters in AD

[Thomas]

when using Active Directoy Authentication for user management, the sendmail process fails with message "Invalid Address".
This happens with all users that have an german umlaut in their common name (not the user name). Sending mails works fine for all users with umlaut.
e.g.: works: username: "hans.meier" common name: "Hans Meier"
fails: username: "dirk.mueller" common name: "Dirk Müller"