ändere die Gruppe doch mal ist doch schnell gemacht ...
Nachtrag:
Note Group entries cannot contain a domain qualifier ('@' sign). For example, an entry for a group with the name DenyMail is valid, but if you add the domain name to the entry, as in Denymail@acme, IBM® Lotus® Domino® does not expand the entry to determine its members. This restriction applies to nested groups also. That is, if the group DenyMail includes Sales@AcmeWest as a member, Domino does not expand Sales@AcmeWest to determine its members