When you send an email (custom letter) to a student or staff, the email is placed in the Letter Queue with a status of "Unprocessed".  You can easily navigate to the letter queue by clicking on Administration | Communication | Queue.

 

Studioware processes items in the letter queue every 20 minutes.  Please note, you can cancel "Unprocessed" email requests from the letter queue anytime prior to them being processed.  The letter queue appears as follows:

 

 

The letter queue will show you when the request was made, the current status, the staff member that made the request, and various information about the request being made.

 

After the email request is completed processing, the status will switch to "Completed".  The "Recipients" column will show you the number of students (or staff) that are being emailed.  The "Queue Emails" column shows the number of emails that were submitted for delivery:

 

In the example above, the "composed letter" is being sent to 1 student.  The one student happens to have 3 email addresses defined on the student record.  Additionally, none of the 3 emails on the student account have "Unsubscribed".

 

Upon clicking on the "Details" link, additional information can be seen on the delivery of the emails:

 

 

The pie chart shows the "Email Results" of the 3 email delivered to the 1 recipient.  The sent emails are tracked by Studioware.   We see that one of the emails was "Opened" by the recipient, and the other 2 emails have been delivered.