Until now, there has only been one way to control whether or not a new message is posted to email: by setting the message's label to one which is admin-only. Even then, the message would still be sent to all of the administrators (but not regular members).
Terry Frazier has sponsored a new (little) feature: a new msg macro that inserts a checkbox to control whether or not the message is posted to email. By default, the checkbox is checked, meaning the message will be posted to email. Uncheck it before submitting the message, and the message won't go out in email.
The macro has been added to the READONLY message editing templates, like this:
<!--#if condition="userIsConvAdmin"--><p><span class="msgToolbarCell msgToolbarText"><!--#msgPostToEmail--></span></p><!--#endIf-->
We assume that you, as the administrator of your site, won't want to confuse your users by showing this checkbox to everybody. Thus, it's wrapped in that conditional macro, so that it only shows up for administrators.
(Otherwise, some users will uncheck it when they shouldn't have, and anyone reading the conversation in email will miss some messages.)
The intended use for this macro is for an admin to post a message to the site which truly should not go out in email: structural messages, long or incomplete messages, etc.
Another benefit is that it's immediately available, and it's meaning is immediately clear even to "new" administrators. Using a label to control posting to the mailing list was never very well received because it wasn't obvious.
I hope you all find this useful.
Seth