Setting up faxing (AudioCodes MP1288) in Zoom

This post was most recently updated on July 23rd, 2022

With the AudioCodes MP1288 gateway connected to a fax machine, it is possible to set up fax support.

Note: It is recommended that you take a look at FaxSIPit as an alternative to Zoom Phone for faxing.


  • Ownership or admin privileges on an account
  • License for Zoom Phone
  • Connected to a fax machine through a provisioned AudioCodes MP1288 gateway

Note: It is not covered in this document how to set up and provision the MP1288 device. For a quick and easy setup of the AudioCodes MP1288 gateway, please refer to the quick start guide. We are assuming that you already have analog ports configured, and calls to and from the analog ports are working as described in this guide. After that, the Analog port will be assigned the Fax parameters for the Fax that are already configured on that port.

Limitations of fax over Voice over Internet Protocol (VoIP)

In the implementation of fax over VoIP services, there are known limitations to faxing. There are a number of technological limitations that apply across the industry and are based on technology. For the purpose of sending faxes over the Internet, Zoom and several VoIP companies make use of the G.711 standard. It is vital to understand, however, that regardless of how reliable that standard may be, it remains open to interpretation by various providers and cannot be guaranteed to be implemented end-to-end.

An analog terminal adapter (ATA) connects a traditional fax machine to the internet via Zoom’s fax over VoIP service, which provides a way to connect a conventional fax machine to the Internet. The best-effort fax service is a cost-effective and more than adequate option for many of our business customers who want to occasionally perform a faxing operation for a small fee. The best way to determine the best faxing solution for your business is to assess your faxing needs.

There are a number of things that Zoom is concerned about, including providing you with quality services for your business. The best way to ensure reliable and consistent fax delivery is to maintain an analog line and a traditional fax machine in case your business relies heavily on faxing large, multi-page documents on a regular basis.

How to set up faxing

  1. You will need to sign in to the MP1288 web interface.
  2. On the SIGNALING & MEDIA tab, click the SIGNALING & MEDIA button.
  3. To set up fax/modem/CID settings, click MEDIA on the left-hand navigation panel and then click Fax/Modem/CID Settings.
  4. You will need to change the following fields from Events Only to Events Only:
    • Fax Transport Mode
    • V.21 Modem Transport Type
    • V.22 Modem Transport Type
    • V.23 Modem Transport Type
    • V.32 Modem Transport Type
    • V.34 Modem Transport Type
  5. Please make the following changes to the following fields as specified below:
    • Fax Relay Max Rate (bps): 9600bps
    • Fax/Modem Bypass Coder Type: G711Ulaw or G711Alaw, depending on region
  6. When you are done, click on the Apply button.
  7. Select CODERS & PROFILES from the left-side menu and then click on ‘Coder Groups‘ in the left-side navigation panel.
  8. In the Coder Group Name field, ensure that AudioCodersGroup_0 is listed at the top of the page with the following coders listed as members.
    Coder Name Packetization Time Rate Payload Type Silence Suppression
    Opus 20 N/A 111 N/A
    G722 20 64 9 Disabled
    G.711U0-law 20 64 0 Disabled
    G.711A-law 20 64 8 Disabled
  9. With the following codes in place, make a new Coder Group named AudioCodersGroup_1 with the following details.
    Note: In this group, make sure that only the G711U-laws and G711A-laws are included. As a result, the G711 codec will be forced to be used for faxes.
  10. Coder Name Packetization Time Rate Payload Type Silence Suppression
    G.711U-law 20 64 0 Disabled
  11. Then click on the Apply button.
  12. The following fields should be included in the Tel-Profile when creating it:
      • Name: Identify the Zoom room display. If the video is off, this will show or hide your name or profile by giving it a name, such as Fax Profile, so that it can be identified.
      • Profile Preference: 1
      • Fax Signaling Method: No Fax
      • Enable Digit Delivery: Disable
      • Dial Plan Index: -1
      • Call Priority: Disable
      • Coders Group: Select AudioCodersGroup_1 created in step 8
      • RTP IP DiffServ: 46
      • Signaling DiffServ: 24
      • Enable Early Media: Disable
      • Echo Canceler: Line Echo Canceller
      • EC NLP Mode: Adaptive NLP
  13. Then click on the “Apply” button.
  14. You can access trunk Contacts and Channels . You can add contacts, create contact groups by clicking GATEWAY > Trunks & Groups > Trunk Groups in the navigation panel.
  15. Each port that will be used to connect a fax machine to the phone network should have the Tel Profile Name column filled in with the name created in step 11.
  16. Then click on the Apply button.
  17. Click on the Save button at the top right of the page when you are done editing.