Refactoring

app/src/main/java/eu/faircode/email/Core.java

@@ -3914,9 +3914,9 @@ class Core {
                     if (r != null) {
                         String label = null;
                         if (r.isDeliveryStatus())
-                            label = (r.isDelivered() ? "$Delivered" : "$NotDelivered");
+                            label = (r.isDelivered() ? MessageHelper.FLAG_DELIVERED : MessageHelper.FLAG_NOT_DELIVERED);
                         else if (r.isDispositionNotification())
-                            label = (r.isDisplayed() ? "$Displayed" : "$NotDisplayed");
+                            label = (r.isDelivered() ? MessageHelper.FLAG_DISPLAYED : MessageHelper.FLAG_NOT_DISPLAYED);
 
                         if (label != null) {
                             Map<Long, EntityFolder> map = new HashMap<>();

app/src/main/java/eu/faircode/email/MessageHelper.java

@@ -163,6 +163,10 @@ public class MessageHelper {
     static final String FLAG_NOT_JUNK = "$NotJunk";
     static final String FLAG_CLASSIFIED = "$Classified";
     static final String FLAG_FILTERED = "$Filtered";
+    static final String FLAG_DELIVERED = "$Delivered";
+    static final String FLAG_NOT_DELIVERED = "$NotDelivered";
+    static final String FLAG_DISPLAYED = "$Displayed";
+    static final String FLAG_NOT_DISPLAYED = "$NotDisplayed";
 
     // https://www.iana.org/assignments/imap-jmap-keywords/imap-jmap-keywords.xhtml
     // Not black listed: Gmail $Phishing