diff --git a/app/src/main/java/eu/faircode/email/MessageClassifier.java b/app/src/main/java/eu/faircode/email/MessageClassifier.java
index aaedf12d69..7f66276f9b 100644
--- a/app/src/main/java/eu/faircode/email/MessageClassifier.java
+++ b/app/src/main/java/eu/faircode/email/MessageClassifier.java
@@ -39,7 +39,7 @@ import java.util.Collections;
 import java.util.Comparator;
 import java.util.Date;
 import java.util.HashMap;
-import java.util.HashSet;
+import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 
@@ -282,47 +282,37 @@ public class MessageClassifier {
 
             for (String clazz : classFrequency.keySet()) {
                 Frequency frequency = classFrequency.get(clazz);
+                if (frequency.count > 0) {
+                    Stat stat = state.classStats.get(clazz);
+                    if (stat == null) {
+                        stat = new Stat();
+                        state.classStats.put(clazz, stat);
+                    }
 
-                Stat stat = state.classStats.get(clazz);
-                if (stat == null) {
-                    stat = new Stat();
-                    state.classStats.put(clazz, stat);
+                    int c = frequency.count;
+                    Integer b = (before == null ? null : frequency.before.get(before));
+                    Integer a = (after == null ? null : frequency.after.get(after));
+                    stat.totalFrequency +=
+                            ((b == null ? 0.0 : (double) b / c) + c + (a == null ? 0.0 : (double) a / c)) / 3;
+
+                    stat.matchedWords++;
+                    if (stat.matchedWords > state.maxMatchedWords)
+                        state.maxMatchedWords = stat.matchedWords;
+
+                    if (BuildConfig.DEBUG)
+                        stat.words.add(current);
                 }
-
-                stat.matchedWords++;
-
-                boolean b = (before != null && frequency.before.contains(before));
-                boolean a = (after != null && frequency.after.contains(after));
-                if (b && a)
-                    stat.totalFrequency += frequency.count;
-                else if (b || a)
-                    stat.totalFrequency += frequency.count * 0.5;
-                else
-                    stat.totalFrequency += frequency.count * 0.25;
-
-                if (BuildConfig.DEBUG)
-                    stat.words.add(current);
-
-                if (stat.matchedWords > state.maxMatchedWords)
-                    state.maxMatchedWords = stat.matchedWords;
             }
 
             Frequency c = classFrequency.get(currentClass);
             if (c == null)
                 c = new Frequency();
-            c.count++;
-            if (before != null && !c.before.contains(before))
-                c.before.add(before);
-            if (after != null && !c.after.contains(after))
-                c.after.add(after);
+            c.add(before, after, 1);
             classFrequency.put(currentClass, c);
         } else {
             Frequency c = (classFrequency == null ? null : classFrequency.get(currentClass));
             if (c != null)
-                if (c.count > 0)
-                    c.count--;
-                else
-                    classFrequency.remove(currentClass);
+                c.add(before, after, -1);
         }
     }
 
@@ -411,11 +401,11 @@ public class MessageClassifier {
         return jroot;
     }
 
-    private static JSONArray from(HashSet<String> list) {
-        JSONArray jarray = new JSONArray();
-        for (String item : list)
-            jarray.put(item);
-        return jarray;
+    private static JSONObject from(Map<String, Integer> map) throws JSONException {
+        JSONObject jmap = new JSONObject();
+        for (String key : map.keySet())
+            jmap.put(key, map.get(key));
+        return jmap;
     }
 
     static void fromJson(JSONObject jroot) throws JSONException {
@@ -443,30 +433,50 @@ public class MessageClassifier {
             Frequency f = new Frequency();
             f.count = jword.getInt("frequency");
             if (jword.has("before"))
-                f.before = from(jword.getJSONArray("before"));
+                f.before = from(jword.getJSONObject("before"));
             if (jword.has("after"))
-                f.after = from(jword.getJSONArray("after"));
+                f.after = from(jword.getJSONObject("after"));
             classFrequency.put(jword.getString("class"), f);
         }
     }
 
-    private static HashSet<String> from(JSONArray jarray) throws JSONException {
-        HashSet<String> result = new HashSet<>(jarray.length());
-        for (int i = 0; i < jarray.length(); i++)
-            result.add((String) jarray.get(i));
+    private static Map<String, Integer> from(JSONObject jmap) throws JSONException {
+        Map<String, Integer> result = new HashMap<>(jmap.length());
+        Iterator<String> iterator = jmap.keys();
+        while (iterator.hasNext()) {
+            String key = iterator.next();
+            result.put(key, jmap.getInt(key));
+        }
         return result;
     }
 
     private static class State {
-        int maxMatchedWords = 0;
-        List<String> words = new ArrayList<>();
-        Map<String, Stat> classStats = new HashMap<>();
+        private int maxMatchedWords = 0;
+        private List<String> words = new ArrayList<>();
+        private Map<String, Stat> classStats = new HashMap<>();
     }
 
     private static class Frequency {
-        int count;
-        HashSet<String> before = new HashSet<>();
-        HashSet<String> after = new HashSet<>();
+        private int count = 0;
+        private Map<String, Integer> before = new HashMap<>();
+        private Map<String, Integer> after = new HashMap<>();
+
+        private void add(String b, String a, int c) {
+            if (count + c < 0)
+                return;
+
+            count += c;
+
+            if (b != null) {
+                Integer x = before.get(b);
+                before.put(b, (x == null ? 0 : x) + c);
+            }
+
+            if (a != null) {
+                Integer x = after.get(a);
+                after.put(a, (x == null ? 0 : x) + c);
+            }
+        }
     }
 
     private static class Stat {
@@ -476,10 +486,10 @@ public class MessageClassifier {
     }
 
     private static class Chance {
-        String clazz;
-        Double chance;
+        private String clazz;
+        private Double chance;
 
-        Chance(String clazz, Double chance) {
+        private Chance(String clazz, Double chance) {
             this.clazz = clazz;
             this.chance = chance;
         }