Update new messages every 15 seconds during sync

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

@@ -135,6 +135,7 @@ public class ServiceSynchronize extends ServiceBase implements SharedPreferences
 
     static final int DEFAULT_BACKOFF_POWER = 3; // 2^3=8 seconds (totally 8+2x20=48 seconds)
 
+    private static final long MSG_DELAY = 15 * 1000L; // milliseconds
     private static final long BACKUP_DELAY = 30 * 1000L; // milliseconds
     private static final long PURGE_DELAY = 30 * 1000L; // milliseconds
     private static final int QUIT_DELAY = 10; // seconds
@@ -737,6 +738,15 @@ public class ServiceSynchronize extends ServiceBase implements SharedPreferences
 
         final TwoStateOwner cowner = new TwoStateOwner(this, "liveSynchronizing");
 
+        final Runnable updateNew = new Runnable() {
+            @Override
+            public void run() {
+                Log.i("Update new messages");
+                cowner.restart();
+                getMainHandler().postDelayed(this, MSG_DELAY);
+            }
+        };
+
         db.folder().liveSynchronizing().observe(this, new Observer<List<TupleFolderSync>>() {
             private List<Long> lastAccounts = new ArrayList<>();
             private List<Long> lastFolders = new ArrayList<>();
@@ -776,10 +786,13 @@ public class ServiceSynchronize extends ServiceBase implements SharedPreferences
                         " folders=" + folders.size() +
                         " accounts=" + accounts.size());
 
-                if (syncing == 0)
+                if (syncing == 0) {
+                    getMainHandler().removeCallbacks(updateNew);
                     cowner.start();
-                else
+                } else {
                     cowner.stop();
+                    getMainHandler().postDelayed(updateNew, MSG_DELAY);
+                }
 
                 if (!changed)
                     return;