CMX is legacy and read-only here
CMX is an older vector format. It can usually be opened and converted from, but it's long obsolete, so there's no modern encoder to create new CMX files.
Looking for DXF to CMX? Here's why CMX isn't an output option — and the modern formats to use.
We don't create CMX files — it's a legacy format that's effectively read-only. Here's what to convert to instead.
CMX is an older vector format. It can usually be opened and converted from, but it's long obsolete, so there's no modern encoder to create new CMX files.
For a file that opens everywhere, convert your DXF to SVG, PDF or EPS instead.
DXF is an open CAD interchange format nearly every CAD program reads — common for CNC and laser cutting.
How to open DXF opens in virtually all CAD software plus CNC and laser tools.
Full DXF format guide