Actually, given vbulletin's code, I'm not sure it's possible to enable it JUST to contact specific members (e.g. Mods and admins). Seems like we looked at that once long ago, and it didn't fly on code reasons. Can't hurt to posit it to those more "in the know."
I know that one thing that just now struck me is to see if vbulletin, or another company, offers some kind of "form e-mail" software -- a web page where you enter the e-mail contents, and it does it for you. Bad news is, I believe e-mail services were turned off the server to counter soem sort of spam-hijack a while back.