diff --git a/app/src/main/java/eu/faircode/email/MessageClassifier.java b/app/src/main/java/eu/faircode/email/MessageClassifier.java
index 1e67b69e73..6f7f6fdf72 100644
--- a/app/src/main/java/eu/faircode/email/MessageClassifier.java
+++ b/app/src/main/java/eu/faircode/email/MessageClassifier.java
@@ -26,6 +26,9 @@ import android.text.TextUtils;
 import androidx.preference.PreferenceManager;
 
 import org.jetbrains.annotations.NotNull;
+import org.json.JSONArray;
+import org.json.JSONException;
+import org.json.JSONObject;
 
 import java.io.File;
 import java.io.IOException;
@@ -38,6 +41,7 @@ import java.util.List;
 import java.util.Map;
 
 public class MessageClassifier {
+    private static boolean loaded = false;
     private static Map<String, Integer> classMessages = new HashMap<>();
     private static Map<String, Map<String, Integer>> wordClassFrequency = new HashMap<>();
 
@@ -45,10 +49,15 @@ public class MessageClassifier {
     private static final double CHANCE_THRESHOLD = 2.0;
 
     static String classify(EntityMessage message, boolean added, Context context) {
-        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
-        if (!prefs.getBoolean("classify", BuildConfig.DEBUG))
+        if (!isEnabled(context))
             return null;
 
+        try {
+            load(context);
+        } catch (Throwable ex) {
+            Log.e(ex);
+        }
+
         DB db = DB.getInstance(context);
 
         EntityFolder folder = db.folder().getFolder(message.folder);
@@ -198,6 +207,87 @@ public class MessageClassifier {
         return classification;
     }
 
+    static synchronized void save(Context context) throws JSONException, IOException {
+        if (!isEnabled(context))
+            return;
+
+        JSONArray jmessages = new JSONArray();
+        for (String clazz : classMessages.keySet()) {
+            JSONObject jmessage = new JSONObject();
+            jmessage.put("class", clazz);
+            jmessage.put("count", classMessages.get(clazz));
+            jmessages.put(jmessage);
+        }
+
+        JSONArray jwords = new JSONArray();
+        for (String word : wordClassFrequency.keySet())
+            for (String clazz : wordClassFrequency.get(word).keySet()) {
+                JSONObject jword = new JSONObject();
+                jword.put("word", word);
+                jword.put("class", clazz);
+                jword.put("frequency", wordClassFrequency.get(word).get(clazz));
+                jwords.put(jword);
+            }
+
+        JSONObject jroot = new JSONObject();
+        jroot.put("messages", jmessages);
+        jroot.put("words", jwords);
+
+        File file = getFile(context);
+        Helper.writeText(file, jroot.toString(2));
+
+        loaded = false;
+        Log.i("Classifier saved classes=" + classMessages.size() + " words=" + wordClassFrequency.size());
+    }
+
+    private static synchronized void load(Context context) throws IOException, JSONException {
+        if (loaded)
+            return;
+
+        if (!isEnabled(context))
+            return;
+
+        classMessages.clear();
+        wordClassFrequency.clear();
+
+        File file = getFile(context);
+        if (file.exists()) {
+            String json = Helper.readText(file);
+            JSONObject jroot = new JSONObject(json);
+
+            JSONArray jmessages = jroot.getJSONArray("messages");
+            for (int m = 0; m < jmessages.length(); m++) {
+                JSONObject jmessage = (JSONObject) jmessages.get(m);
+                classMessages.put(jmessage.getString("class"), jmessage.getInt("count"));
+            }
+
+            JSONArray jwords = jroot.getJSONArray("words");
+            for (int w = 0; w < jwords.length(); w++) {
+                JSONObject jword = (JSONObject) jwords.get(w);
+                String word = jword.getString("word");
+                Map<String, Integer> classFrequency = wordClassFrequency.get(word);
+                if (classFrequency == null) {
+                    classFrequency = new HashMap<>();
+                    wordClassFrequency.put(word, classFrequency);
+                }
+                classFrequency.put(jword.getString("class"), jword.getInt("frequency"));
+            }
+        }
+
+        loaded = true;
+        Log.i("Classifier loaded classes=" + classMessages.size() + " words=" + wordClassFrequency.size());
+    }
+
+    private static boolean isEnabled(Context context) {
+        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
+        return prefs.getBoolean("classify", BuildConfig.DEBUG);
+    }
+
+
+    private static File getFile(Context context) {
+        return new File(context.getFilesDir(), "classifier.json");
+    }
+
     private static class Stat {
         int matchedWords = 0;
         int totalFrequency = 0;
diff --git a/app/src/main/java/eu/faircode/email/ServiceSynchronize.java b/app/src/main/java/eu/faircode/email/ServiceSynchronize.java
index 0945902e19..5eef492079 100644
--- a/app/src/main/java/eu/faircode/email/ServiceSynchronize.java
+++ b/app/src/main/java/eu/faircode/email/ServiceSynchronize.java
@@ -735,6 +735,17 @@ public class ServiceSynchronize extends ServiceBase implements SharedPreferences
 
         liveAccountNetworkState.postDestroy();
 
+        executor.submit(new Runnable() {
+            @Override
+            public void run() {
+                try {
+                    MessageClassifier.save(ServiceSynchronize.this);
+                } catch (Throwable ex) {
+                    Log.e(ex);
+                }
+            }
+        });
+
         TTSHelper.shutdown();
 
         try {