Hi Rafael,
I'm afraid I didn't get an answer to this. I ended up having to persuade our client to let me have the base domain.
I'd still like to know if it is possible, or at least get confirmation that it isn't possible.
Thanks for your reply Andrew,
I have got the LetsEncrypt extension and I've used it many times.
But on this occasion my client has given me access to {mydomain} but not to www.{mydomain}.
Plesk is trying to install the LetsEncrypt certificate on {mydomain} and giving me www.{mydomain} as an...
I have a website on www.{mydomain}, but I don't have access to {mydomain}.
Because of this I can't install LetsEncrypt because it is trying to access {mydomain}/.well-known/acme-challenge/...
Is it possible to install a LetsEncrypt certificate when I don't have access to {mydomain}?
I did...