Site admin contact member blog owners?

What is the best method for the site owner to contact member blog owners? I want to send out helpful tips and helps about maintaining member blogs and offering support for the site. How can I send that info through the admin area? Would that be best?

Idea: A Blog Basic How To that would explain to new member blog owners the do's and don't's of the admin area. This could be a pop-up or an admin note area of each site owner? Maybe create a plug-in that allows a note to either all or some of the blog owners (can be a check make beside each name) sends a simple email explaining that they have an admin note waiting from the Site Administrator?