When I installed openSUSE on my laptop I chose the XFCE desktop environment. Along with that came Thunar file manager. Later when when I installed MATE 1.6 I noticed that Thunar was still my default file manager. I wanted to set Caja as default file manager. I went through the System > Control Center > File Manager, but there wasn’t any option to set the default file manager.
I spent some time searching if YaST can help here but nope! I googled a bit to set the same by editing the config files.
Finally the solution came with MATE settings while I was looking at the MATE command line utilities. So, to set Caja as default file manager, press Alt + F2 and run mate-default-applications-properties.
The following dialog box will pop up:
Click on the System tab and from the drop-down menu under File Manager select Caja.
To make it look even greater I’m using Mint-X (MATE theme) from Linux Mint.