SkyeFax (T.38) and Fax Machines


SkyeFax (T.38) works with all fax machines that use standard sub 14,400 baud rate faxing. By and large, this should account for the very vast majority of fax machines. There are some fax machines that are able to transmit faster than 14,400 baud, and are often shipped from the manufacturer with the faster speeds enabled by default. Unfortunately, the T.38 protocol used by carriers (and, more importantly, ATA devices) cannot go faster than 14,400, and so those machines will not work with SkyeFax (T.38) unless you configure them to use 14,400 baud or lower. 

The industry refers to this super-fast protocol as Super G3, and your Fax Machine may refer to it as V.34 or V.8. In any case, we need to disable it for your fax machine to work correctly.

Configuring Your Fax Machine

To make your fax machine work, you will want to find and disable these settings on your fax machine. Each fax machine is different, but typically they will refer to this setting simply as "Fax Speed." The SkyeFax (T.38) caching layer is designed to work at 14,400, and can be paired down to 9,600 if your particular fax machine likes to go slowly.

Most manufactures use different nomenclature here, but this should help you find the setting you are looking for. We recommend you set your Fax Machine to 14,400, and lower it to slow if you have deliverability issues. 

Hewlett Packard

  • Fast - 33,600bps
  • Medium - 14,400bps
  • Slow- 9,600bps


  • Fast - 33,600bps
  • Medium - 14,400bps
  • Slow- 9,600bps


  • High - 33,600bps
  • Normal - 14,400 bps
  • Basic - 9,600 bps

Testing your Fax Machine

We recommend you test your fax machine by sending and receiving a 5 page fax 3 times. Successful testing should be done by using a third party fax machine if possible, and where not, using a third party web service. We recommend using FaxZero to test receiving of faxes. Do not send a fax from SkyeFax (T.38) to a SkyeFax ATA (T.38); doing so will not give you a real world test. 

Where possible, we also recommend avoiding changing ATA settings. The ATA settings provided for in our documentation have been thoroughly tested against a variety of Fax Machines (including our tests over satellite internet connections).

Please note - Skyetel Support will not be able to generate test faxes for your use case. We strongly recommend you create a thorough fax scheding routine that you use before you put faxes into deployment.


Unfortunately, Fax machines are fickle. The best way to test a fax machine is to send a bunch of faxes to it over and over again to verify that it is working correctly. We recommend sending a 10 page fax 3 times before putting the fax machine into production. Make sure you recycle the paper afterwards!

If your fax machine continues to have deliverability issues, we recommend lowering the fax machine's baud rate from 14,400 to 9,600. While many docs online will tell you to disable ECM (error correction mode) on the fax machine, we don't recommend that unless its the last resort. In fact - if you have to disable ECM , its probably a good idea to replace the fax machine all together. ECM its part of what makes T.38 faxing work reliably. 

Replacing Your Fax Machine

If all else fails, don't rule out replacing your fax machine. If you are in the process of replacing existing telecom equipment, it is recommended that you use a fax machine you have tested thoroughly for use for SkyeFax (T.38). 

Our current favorite is the Brother MFC 9130CW, but yours may differ. 


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