Works flawlessly for me ...

For an occassional Fax user, this turned out to be the right tools for me.
I am using iFax Version 1.10.10 (1.10.17) over Yosemite (OSX rev 10.10.5)

Pros:
- Clean, clutter free, easy to use user-interface
- So far delivered all of my my out faxes on the first try.

Not so thrilled:
- Bills me $1.99 for a 9 page long Outgoing Fax, could get expensive for frequent user ...

Proy, The Contrarian about Send & Receive Fax App- iFax