When I invite a new user - see https://support.atlassian.com/user-management/docs/invite-a-user/ - I can send him an individual invite message.
I would like to do the same if someone requests access to our site and I approve this request - see https://support.atlassian.com/user-management/docs/approve-or-deny-product-access-requests/
However I cannot find a way to do this.
We use the individual invite message to provide the new users with information about how we are using the Altassian products, whom to contact for support and direct him to additional ressources.