I imagine most forum software developers include this feature. Most of these forum developers have support forums on their site. For example: http://www.phpbb.com/community/
So, I suggest you look for a support forum for the forums you are considering and post your question there.
Clearly, vBulletin has that feature. It's being used right here, in this forum.
Here's message that appears:
Thank you for posting! Your post will not be visible until a moderator has approved it for posting.