CMC shouldn't be loading mootools. It's been removed since a lot of time. What kind of a subscribe form do you have? just email and name? Or more exotic fields?

CMC is used on our start page and we don't load mootools.

We use email, name and 1 field for language

Any idea how i can fix this

So, you unpublish the cmc module - and mootools is no longer being loaded on the page?

If that is the case - are you sure that you don't have any old cmc overrides?

I have checked and found no old overrides for cmc

Then I'm out of ideas. So you disable the module and mootools immediately disappears from the page?