The contacts and groups are managed in isolated accounts each representing a Team. A Team is a generic term for organisation units, common interest groups, sports clubs, external businesses, like suppliers or customers. Even a family or some friends may be represented by a Team. Team members can share some of their mutually maintained contacts. Of course, sharing information is completely voluntary. It is assumed that only Team related information will be shared and different Teams do not impact each other in any way. Contacts managed by a Team are stored on devices of Team members and information will be synchronized in real-time by the separately available Contacts Sync for Teams app (currently in work, will be published soon). The contacts are sensitive data and they are protected by zero-knowledge encryption.