[Mailman-Users] Site administrative broadcast to all lists and all list members - server wide

I have searched for a way to send a "server-wide" broadcast message to all admins and subscribers and found the following (which I have yet to try):

"Send a message with an Urgent: header that contains the admin password and it's supposed to be sent as a direct message to all subscribers"

What I find a but confusing is how to specify an "Urgent" header. Does this person mean to say place "Urgent" in the subject line with the Admin password? In other words, I am not sure how to specify or manipulate a message's "header" with Mailman.

Anybody have any ideas/thoughts or am I missing something obvious?

Thanks for any and all help - Brandon