Birchfax
This software requires Node and node-phaxio
https://www.dyclassroom.com/howto-mac/how-to-install-nodejs-and-npm-on-mac-using-homebrew https://github.com/chadsmith/node-phaxio
Add the workflow to your system by copying or moving the file "Birchfax Workflow" to your ~/Library/Automator folder. If this folder does not already exist, you'll need to create one.
Create a folder (in Home might be good) called Faxes. In Faxes, create two folders, Outbox and Sent.
Right-click the Outbox folder, go to Services, and pick Folder Actions Setup
Choose "Birchfax"
If you like, you can create an alias to Outbox and put it somewhere convenient like your Desktop.