Alice Corporate 
In the "Manage Service", "Ip Routes" web page configure the following parameters.
- Protocol: SIP
- Negotiation: Allow G.711 for outgoing faxes
- Network routing type: Both offnet and on-net
- Off-net pattern: Enter the common prefix to reach the PSTN
- PBX Routing Type: Per user
Edit the default route so that it points to the PBX.
In the user's management configure the "Fax Routing Prefix" and "Fax Off-net Number" as required.
Impresa semplice
In the "Manage Service", "Ip Routes" web page configure the following parameters:
- Protocol: SIP
- Negotiation: Allow G.711 for outgoing faxes, Disable T.38 for incoming faxes
- Network routing type: Extenal (offnet) faxes only
- PBX Routing Type: Global
- Prefix to the called number: enter 0 if needed to reach the PSTN
Edit the default route so that it points to the PBX.
In the user's management configure "Fax Off-net Number" as required.
Unigate - FastWeb 
In the "Manage Service", "Ip Routes" web page, configure the following parameters:
- Protocol: SIP
- Negotiation: No selection (Allow G.711 UNCHECKED and Disable T.38 UNCHECKED)
- Network routing type: External (offnet) faxes only
- PBX Routing Type: Global
- Prefix to the called number: enter 0 if needed to reach the PSTN
