Index: assignment-impl/impl/src/java/org/sakaiproject/assignment/impl/BaseAssignmentService.java
===================================================================
--- assignment-impl/impl/src/java/org/sakaiproject/assignment/impl/BaseAssignmentService.java	(revision 115004)
+++ assignment-impl/impl/src/java/org/sakaiproject/assignment/impl/BaseAssignmentService.java	(working copy)
@@ -32,6 +32,7 @@
 import java.util.Collection;
 import java.util.Comparator;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Locale;
@@ -2406,23 +2407,40 @@
 
 	} // commitEdit(Submission)
 	
-	protected void sendGradeReleaseNotification(boolean released, String notificationSetting, User[] submitters, AssignmentSubmission s)
+	protected void sendGradeReleaseNotification(boolean released, String notificationSetting, User[] allSubmitters, AssignmentSubmission s)
 	{
+		if (allSubmitters == null) return;
+		
+		// SAK-19916 need to filter submitters against list of valid users still in site
+		Set<User> filteredSubmitters = new HashSet<User>();
+		try {
+			String siteId = s.getAssignment().getContext();
+			Set<String> siteUsers = SiteService.getSite(siteId).getUsers();
+
+			for (int x = 0; x < allSubmitters.length; x++)
+			{
+				User u = (User) allSubmitters[x];
+				String userId = u.getEid();
+				if (siteUsers.contains(userId)) {
+					filteredSubmitters.add(u);
+				}
+			}
+		} catch (IdUnusedException e) {
+			// TODO Auto-generated catch block
+			e.printStackTrace();
+		}
+		
+		User[] submitters = new User[filteredSubmitters.size()];
+		filteredSubmitters.toArray(submitters);
+		
 		if (released && notificationSetting != null && notificationSetting.equals(Assignment.ASSIGNMENT_RELEASEGRADE_NOTIFICATION_EACH))
 		{
-			// send email to every submitters
-			if (submitters != null)
-			{
 				// send the message immidiately
 				EmailService.sendToUsers(new ArrayList(Arrays.asList(submitters)), getHeaders(null, "releasegrade"),  getNotificationMessage(s, "releasegrade"));
-			}
 		}
 		if (notificationSetting != null && notificationSetting.equals(Assignment.ASSIGNMENT_RELEASERESUBMISSION_NOTIFICATION_EACH)){
-			// send email to every submitters
-			if (submitters != null){
 				// send the message immidiately
 				EmailService.sendToUsers(new ArrayList(Arrays.asList(submitters)), getHeaders(null, "releaseresumbission"),  getNotificationMessage(s, "releaseresumbission"));
-			}
 		}
 	}