Some VoIP services need additional configuration to be able to successfully send fax transmissions, as they require higher bandwidth, almost no packet loss, and support for special protocols. Still, it is usually possible to send and receive faxes with the proper equipment and configuration.
Below are some general steps that can help you setup your equipment correctly:
1. Configure your fax machine - many modern devices have configuration options for fax compatibility. It is a good idea to set the following in your fax machine for VoIP compatibility in general:
- reduce baud rate to 9600 (if available)
- turn off ECM (error correction mode). In some models, this is accomplished by turning on "Overseas mode".
- set your device for "Basic fax compatibility" (if available) when using VoIP.
2. Dial *99 (or *98) prefix to configure Ooma - the Ooma service needs to know that you are attempting to send a fax, so the connection can be optimized for fax transmissions. First, dial the prefix *99 before dialing the fax number you wish to reach. With the newer Ooma Telo devices, you can try dialing *98 before the fax number instead ( *99 should be automatically detected by the system)
3. Disable QoS in the Ooma device - If you are still having issues sending faxes, try disabling the QoS in the Ooma Hub/Telo. In your browser, navigate to the IP of your Ooma device, then click on "Network > Advanced", under Quality of Service make sure to enter zero for both "Upstream" and "Downstream" internet speed:
Quality of Service:
Upstream Internet Speed (Kbps): 0
Downstream Internet Speed (Kbps): 0
4. Enable redundancy in the my.ooma.com preferences - login to your my.ooma.com page using your phone number/password, and change the "Premium Faxing Service" to: 3 redundancy.
Note: It may help to enter a "pause" after dialing *99 and before the dialing the fax number you're trying to reach, so that there is dial tone before entering the number. Check your particular fax machine for instructions. (Brother MFCs use the "Redial/Pause" button to enter a pause)
