Added documentation about scheduled jobs and cron jobs

email/set-up.md

@@ -164,6 +164,14 @@ will be sent a welcome message. (Note: When users subscribe to multiple
 groups at once, a confirmation email is sent for each group
 separately.) 
 
+Scheduled jobs and cron jobs
+----------------------------
+
+After people have signed up on your mailing list(s), you will want to be able to send them mass mailings. You will also want to automatically handle any bounced email messages. These topics are dealt with in detail in the **Everyday tasks** and **Maintaining Healthy Email Lists** parts of this book, respectively. Here in this section we are going to look at some backend and server options that enable the sending of mass mailings and the bounce handling to happen.
+
+Go to **Administer > System Settings > Scheduled Jobs** and you will see all scheduled jobs that CiviCRM uses to do certain tasks on a regular basis. One such task is the actual sending of mass mailings, which is handled by the **Send Scheduled Mailings** scheduled job. Another task is the processing of bounced emails, for which the **Fetch Bounces** scheduled job is responsible. You will need to enable these two scheduled jobs (and any others that you want to be run on a regular basis). Without these two, CiviMail will not be sending any mailings and will not be processing the bounces.
+
+Now, CiviCRM's scheduled jobs cannot self-trigger themselves. Something on your server has to trigger them. The most common option for this is to set up a cron job on your server. This cron job can trigger one or more (or all) of the scheduled jobs. For more detailed explanations and examples of how to do this, see the [Managing Scheduled Jobs](http://wiki.civicrm.org/confluence/display/CRMDOC/Managing+Scheduled+Jobs) wiki page.
 
 Automated Messages and mailing list management 
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