4PSA VoipNow is the leading Unified Communications system for Service Providers that integrates a powerful IP PBX, supporting voice, video, presence and faxing with instant messaging based on XMPP protocol. 4PSA VoipNow is based on hosting reselling model with four access levels, close to Parallels Plesk model, using a user friendly browser based GUI. 4PSA VoipNow runs on Linux operating systems and requires a physical server or VPS. Service providers can link Parallels Plesk and VoipNow servers together using the VoipNow Plesk Module.