.htaccess - Subdomain with subfolder gets a 404 error

Question

I have multiple subdomains that are working with a redirect, but bad for SEO

RewriteRule ^([a-zA-Z0-9&:_-]+)/actions$ http://$1.actions.mydomain.nl [R=301,L]

I want to redirecting to:

http://$1.mydomain.nl/actions

but here i get a 404 error.

How to make the right rule for this?