Systems and methods for utilizing a PBX identifier of a PBX system in a mobile environment are provided. In exemplary systems, an enhanced DNS server maintains a central registry of PBX identifiers and corresponding locations associated with the PBX identifiers. The corresponding locations may comprise both private and public IP address. When a remote IP device attempts to access their main office PBX system via the PBX identifier, the enhanced DNS server returns the private and public IP addresses in response.