The Announcements tool allows you to send an e-mail to some or all of your students, or to specific groups. to might want to alert them to the addition of a new document, to remind them of a deadline for submission of an assignment or to highlight and share a particularly good piece of work. Sending such e-mail announcements can also serve as a useful prompt to re-engage students who have not visited the site for some time (as long as it's not overdone!).Contacting specific users
In addition to sending a general one to all members of the course, you can send an e-mail to one or more individuals/groups groups. When you create a new announcement, just click Visible to and select users from the left hand lists and and add them as recipients using the arrows.