Announcements can be an effective way to get people's attention.
You can post an announcement when you are the owner of a place (space, project, or
group). Announcements appear in the Communications stream of users following the place,
and in a banner on the home page of the place.
CAUTION:
Users may also get
an email when a new announcement is posted if they have their email notifications
turned on for Communications stream updates. For more about that, be sure to read
Customizing Email Notifications. If you do not want notifications
(Communications stream and email) sent when you create an announcement, be sure to
check the
Do not send notifications box (checked by default).