Actually, there is a plugin conflict with Mymail. When I try to use the rich text editor, no content appear. When I inspect the html code, the tags don’t contain any text. When I disable ACF, there is no problem.
Is it possible to disable ACF on a certain post type (ex: mymail newsletter)?
Yes, when editing the field groups, set the location to be more precise.
I already tried but ACF keeps loading on page where it should not.
For example, I set a custom fields on “Page” AND category X.
But ACF still loads on custom posts type “Newsletter”.