I Use Froxlor for Email-Only. Now I would like to give two of my customers the control to one of my E-Mail-domains in Froxlor.

Or if that is not possible at least move the domain from one customer account to another.

To control a domain from two customers or move it to another customer seems not possible in the interface

How could I achieve this?

define "control of domain"? If it's email only, there is almost no setting relevant (except maybe to allow subdomains as email-domains as well) - everything else is related to http/https

Moving domains between customers must be enabled explicitly in the settings first: Settings -> Panel settings -> Allow moving domains between admins | Allow moving domains between customers

OK. I activated it, but I don't see how to moving domains between customers. (Only between admins)

these are two different settings, see my previous post

Sure, I activated both.

But there was no option in domain settings still.

But I found out, that after log out and logging in again the drop-down to change the customer appeared. (Maybe a bug?)

Thanks