How to setup DKIM with external DNS

Looking at this procedure;
https://www.virtualmin.com/documentation/email/dkim

it states that “Only virtual servers that have both the DNS and email features enabled will have DKIM activated…”

My DNS are not handled by my server. The only information I need to create the record in the DNS zone is the public key. Why is that not possible? Any means to address this situation?

Thanks for help

Responding to lmyself: actually, it works.
The notice is misleading: there is no need for the DNS to be set in the BIND serveur
Just use the selector like “2015._domainkey” as subdomain et copy the public key that appears in the DKIM form after removing the quotes and tabs.