It allows you to send a fully-customizable community bulletin, generated by vBulletin. It can include latest threads, threads with no replies, threads with most replies or views, polls, calendar events, birthdays, polls, and the user's info (username, password, etc.), and a few other things, as well as anything else you wish to add. The system generates a preview based on your settings and then you can add anything into the text box before mailing. You can limit to which usergroups it gets sent, and from which forums information is pulled, and users can opt-out of receiving it.
This is a "Kier" hack

but I have updated it slightly with his permission, and rereleased it in
this thread. You can also look at
this for more info.