A method of managing Internet Protocol, IP, Multimedia Subsystem, IMS, connections between UEs using virtual IMPUs and a plurality of available IMS service providers (16, 18), the method comprising: registering, by a first IMS node, a first wildcard IMS Public User Identity, IMPU, in a first IMS domain responsive to receiving a first registration request message from an enterprise node, EN, wherein the enterprise node is a Session Initiation Protocol, SIP, node and serves as a Private Branch Exchange, PBX; registering, by a second IMS node, a second wildcard IMS Public User Identity, IMPU, in a second IMS domain responsive to receiving a second registration request message from said EN; allocate, by the EN, a virtual IMPU to an UE, which is utilized by the UE to originate and receive IMS session data regardless of the actual IMS domain, the virtual IMPU comprising a virtual domain name chosen by the enterprise and a first username part for said UE; receiving, by the EN, a session initiation request sent by said UE comprising said virtual IMPU; allocating by the EN an IMS service provider out of the first or second IMS providers to said virtual IMPU used in the session initiation request; storing, by the EN, a binding between said virtual IMPU to an explicit IMPU, the explicit IMPU comprising said first username part of said virtual IMPU combined with the domain name of the allocated IMS provider; sending, by the EN, a SIP Invite message comprising the virtual IMPU to the IMS node of said allocated IMS service provider to initiate a session with a destination UE; responsive to receiving said SIP Invite message, said IMS node locating the registration record for said UE, the location record comprising the virtual domain name of the virtual IMPU and based on the information stored in that record, said IMS node establishing the IMS session between the said UE and the destination UE using said explicit IMPU and ignoring the virtual IMPU; wherein the first and second IMS node is a P-CSCF or a S- CSCF. registering, by a first IMS node, a first wildcard IMS Public User Identity, IMPU, in a first IMS domain responsive to receiving a first registration request message from an enterprise node, EN, wherein the enterprise node is a Session Initiation Protocol, SIP, node and serves as a Private Branch Exchange, PBX; registering, by a second IMS node, a second wildcard IMS Public User Identity, IMPU, in a second IMS domain responsive to receiving a second registration request message from said EN; allocate, by the EN, a virtual IMPU to an UE, which is utilized by the UE to originate and receive IMS session data regardless of the actual IMS domain, the virtual IMPU comprising a virtual domain name chosen by the enterprise and a first username part for said UE; receiving, by the EN, a session initiation request sent by said UE comprising said virtual IMPU; allocating by the EN an IMS service provider out of the first or second IMS providers to said virtual IMPU used in the session initiation request; storing, by the EN, a binding between said virtual IMPU to an explicit IMPU, the explicit IMPU comprising said first username part of said virtual IMPU combined with the domain name of the allocated IMS provider; sending, by the EN, a SIP Invite message comprising the virtual IMPU to the IMS node of said allocated IMS service provider to initiate a session with a destination UE; responsive to receiving said SIP Invite message, said IMS node locating the registration record for said UE, the location record comprising the virtual domain name of the virtual IMPU and based on the information stored in that record, said IMS node establishing the IMS session between the said UE and the destination UE using said explicit IMPU and ignoring the virtual IMPU; wherein the first and second IMS node is a P-CSCF or a S- CSCF.