In order to send announcements to individuals that are assigned with an external course, just search for the course in question in your course catalog and click on the Manage course option.
Then, select the Students option and then Send Announcements.
Search the recipients and select them by clicking on the “+” symbol. To complete your announcement, you can write a message in the space provided, add an image/URL or click Upload Attachment to upload documents from your computer. Finally, click Announce.