rename extension on whole file system

Basically I just want to rename any file on my machine starting with a .mml to a .txt.
So starting at my user folder and including all sub folders. I can't get it working. Any hints. Txs

I have to warn you that having Hazel monitor your whole home folder and every file underneath is very resource intensive. Do mml files just pop up anywhere in your filesystem?

Check the sticky article above to do what you want but I really would recommend against doing this. Instead, I'd focus on key areas where these files might first enter the system.

No there would be only certain subsets of directories where I want to limit the renaming to.
I do not see the "Sticky article" that you refer to.

Look at the article at the top of the forums.

I would suggest having Hazel just monitor specific directories. You should minimize the size of the tree you want it to scan.