One more thing to love about Open Source/Free Software:
Maybe each screw doesn't work exactly as you want. But you can hit them with a big enough hammer. And if you have a big enough hammer, every screw is a nail.
Mgetty+sendfax sucks a little in some areas. It supports no class1 faxes (ok, it may do if you rebuild with a switch it says doesn't really work).
Efax sucks a little in some areas. It has no spooling mechanism. It has no way at all to be used decently from windows clients.
So, remix them!
Take efax's efax command (the one that actually sends the faxes), and mgetty+sendfax's sendfax command.
They are quite similar. So, write a tiny shell wrapper that makes efax look like sendfax.
And Voilá. Mgetty+efax, which works on class1 fax/modems ;-)
The wrapper itself is left as an exercise for the reader.