it is not possible to add new users to a domain with umlauts (www.testö.com), the system says "username must have between 4 and 32 characters...). tried it with username "office" on ispconfig 2.2.6 german.
I guess it won't be possible until ISPConfig handles IDN (http://de.wikipedia.org/wiki/Internationalized_Domain_Name). E.g. there must be a conversion to PUNICODE (http://de.wikipedia.org/wiki/Punycode) cause the zonefiles won't contain any ö, etc. but their punicode encoded equivalent.
If you add the domain as punicode, it shall work. If i remember correctly, umlauts are not allowed in linux system usernames at all.
