How to Setup Inbound Fax Routing in 3CX Phone System


  1. This feature is not available in the free edition of 3CX Phone System.
  2. 3CX Phone System does not include a Fax Sending service.
  3. The 3CX Fax Receiving Server is based on the T.38 standard, and requires a compatible T.38 VoIP Gateway or VoIP Provider. The 3CX Fax Receiving Server does not support G.711 for fax. Supported devices for use with the 3CX Fax Receiving Server are listed here you must check this list for a supported device.
  4. 3CX Phone System is configured by default for receiving faxes using a Gateway device. The configuration for receiving faxes with VoIP Providers is different, and therefore it is, in most cases, not currently possible to configure the 3CX Fax Receiving Server to operate with both Gateways and VoIP Providers at the same time.

The receiving of faxes is handled by the 3CX Fax Server. You must configure a line or a DID to be dedicated to fax, so that all fax calls are forwarded to the 3CX Fax Server. The 3CX Fax Server will then receive the fax, convert it to PDF and then email the fax to the configured extension email address. It is important to configure Email Server options from “Settings” > “General” > “Mail Server” tab because the 3CX Fax Server will use these parameters to send the fax mail to the recipient’s mail box.

  • In the 3CX Management Console, enter a name for the DID and enter the number or group of numbers for incoming faxes.
  • Next select the port or DID which will be dedicated to receiving faxes.

  • Select “Send fax to email of extension”.
  • Select to which email address you want to email the received fax. If you select “Default FAX Destination”, the fax will be sent to the email address configured for the virtual fax extension number. Alternatively you can forward faxes to the email address configured for a particular extension. This allows you to create multiple DID rules so as to give people a personal fax extension. You can configure the default email address from the “Fax Machines” page in the Management Console.

You can also setup specific routing for Out of Office hours if needed.

Changing the Fax Credentials

The Fax server operates as a virtual extension and registers to the 3CX Phone System just as a normal extension would. It needs a unique extension number (default 888), an Authentication ID and Authentication Password. To change the Authentication ID and Authentication Password for the 3CX Fax Server do the following:

  • In the 3CX management console, go to the “Fax Machine” page.
  • In the “Fax Server Extension Number” field, specify the fax extension number. Any call forwarded to this extension will be assumed to be a fax and receive a fax tone. This must be a unique extension.
  • Specify the Fax Server Authentication ID and Authentication Password. These credentials will be used by the 3CX Fax Server to login to the SIP server.
  • Restart the 3CX Fax Server service for the changes to take effect.