Flag junk/no junk

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

@@ -1330,10 +1330,21 @@ class Core {
                     imessage.setFlag(Flags.Flag.FLAGGED, false);
 
                 // Mark not spam
-                if (EntityFolder.JUNK.equals(folder.type) &&
-                        ifolder.getPermanentFlags().contains(Flags.Flag.USER)) {
+                if (!copy && ifolder.getPermanentFlags().contains(Flags.Flag.USER)) {
+                    Flags junk = new Flags(MessageHelper.FLAG_JUNK);
                     Flags notJunk = new Flags(MessageHelper.FLAG_NOT_JUNK);
-                    imessage.setFlags(notJunk, true);
+                    List<String> userFlags = Arrays.asList(imessage.getFlags().getUserFlags());
+                    if (EntityFolder.JUNK.equals(target.type)) {
+                        // To junk
+                        if (userFlags.contains(MessageHelper.FLAG_NOT_JUNK))
+                            imessage.setFlags(notJunk, false);
+                        imessage.setFlags(junk, true);
+                    } else if (EntityFolder.JUNK.equals(folder.type)) {
+                        // From junk
+                        if (userFlags.contains(MessageHelper.FLAG_JUNK))
+                            imessage.setFlags(junk, false);
+                        imessage.setFlags(notJunk, true);
+                    }
                 }
             }
 

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

@@ -145,6 +145,7 @@ public class MessageHelper {
     ));
 
     static final String FLAG_FORWARDED = "$Forwarded";
+    static final String FLAG_JUNK = "$Junk";
     static final String FLAG_NOT_JUNK = "$NotJunk";
     static final String FLAG_CLASSIFIED = "$Classified";
     static final String FLAG_FILTERED = "$Filtered";
@@ -153,13 +154,13 @@ public class MessageHelper {
     // Not black listed: Gmail $Phishing
     private static final List<String> FLAG_BLACKLIST = Collections.unmodifiableList(Arrays.asList(
             MessageHelper.FLAG_FORWARDED,
+            MessageHelper.FLAG_JUNK,
             MessageHelper.FLAG_NOT_JUNK,
             MessageHelper.FLAG_CLASSIFIED, // FairEmail
             MessageHelper.FLAG_FILTERED, // FairEmail
             "$MDNSent", // https://tools.ietf.org/html/rfc3503
             "$SubmitPending",
             "$Submitted",
-            "$Junk",
             "Junk",
             "NonJunk",
             "$recent",