diff --git a/app/src/main/java/eu/faircode/email/FragmentMessages.java b/app/src/main/java/eu/faircode/email/FragmentMessages.java
index a55ead18a7..d949d4c34e 100644
--- a/app/src/main/java/eu/faircode/email/FragmentMessages.java
+++ b/app/src/main/java/eu/faircode/email/FragmentMessages.java
@@ -4288,19 +4288,39 @@ public class FragmentMessages extends FragmentBase implements SharedPreferences.
                         OpenPgpApi.ACTION_DECRYPT_VERIFY.equals(data.getAction()))
                     try {
                         String peer = ((InternetAddress) message.from[0]).getAddress();
+                        boolean mutual = false;
+                        byte[] keydata = null;
 
-                        int k = message.autocrypt.indexOf("keydata=");
-                        if (k >= 0) {
-                            String keydata = message.autocrypt.substring(k + 8);
-                            AutocryptPeerUpdate update = AutocryptPeerUpdate.create(
-                                    Base64.decode(keydata, Base64.DEFAULT),
-                                    new Date(message.received),
-                                    true);
-
-                            data.putExtra(OpenPgpApi.EXTRA_AUTOCRYPT_PEER_ID, peer);
-                            data.putExtra(OpenPgpApi.EXTRA_AUTOCRYPT_PEER_UPDATE, update);
+                        // https://autocrypt.org/level1.html#the-autocrypt-header
+                        String[] param = message.autocrypt.split(";");
+                        for (int i = 0; i < param.length; i++) {
+                            int e = param[i].indexOf("=");
+                            if (e > 0) {
+                                String key = param[i].substring(0, e).trim().toLowerCase();
+                                String value = param[i].substring(e + 1);
+                                Log.i("Autocrypt " + key + "=" + value);
+                                switch (key) {
+                                    case "addr":
+                                        break;
+                                    case "prefer-encrypt":
+                                        mutual = value.trim().toLowerCase().equals("mutual");
+                                        break;
+                                    case "keydata":
+                                        keydata = Base64.decode(value, Base64.DEFAULT);
+                                        break;
+                                }
+                            }
                         }
-                    } catch (IllegalArgumentException ex) {
+
+                        if (keydata == null)
+                            throw new IllegalArgumentException("keydata not found");
+
+                        AutocryptPeerUpdate update = AutocryptPeerUpdate.create(
+                                keydata, new Date(message.received), mutual);
+
+                        data.putExtra(OpenPgpApi.EXTRA_AUTOCRYPT_PEER_ID, peer);
+                        data.putExtra(OpenPgpApi.EXTRA_AUTOCRYPT_PEER_UPDATE, update);
+                    } catch (Throwable ex) {
                         Log.w(ex);
                     }
 
diff --git a/app/src/main/java/eu/faircode/email/FragmentOptionsPrivacy.java b/app/src/main/java/eu/faircode/email/FragmentOptionsPrivacy.java
index 542f57edcd..9d35d1be41 100644
--- a/app/src/main/java/eu/faircode/email/FragmentOptionsPrivacy.java
+++ b/app/src/main/java/eu/faircode/email/FragmentOptionsPrivacy.java
@@ -67,6 +67,7 @@ public class FragmentOptionsPrivacy extends FragmentBase implements SharedPrefer
     private SwitchCompat swDisplayHidden;
     private Spinner spEncryptMethod;
     private Spinner spOpenPgp;
+    private SwitchCompat swAutocryptMutual;
     private SwitchCompat swSign;
     private SwitchCompat swEncrypt;
     private SwitchCompat swAutoDecrypt;
@@ -83,7 +84,7 @@ public class FragmentOptionsPrivacy extends FragmentBase implements SharedPrefer
 
     private final static String[] RESET_OPTIONS = new String[]{
             "disable_tracking", "display_hidden",
-            "default_encrypt_method", "openpgp_provider", "sign_default", "encrypt_default", "auto_decrypt",
+            "default_encrypt_method", "openpgp_provider", "autocrypt_mutual", "sign_default", "encrypt_default", "auto_decrypt",
             "secure",
             "biometrics", "pin", "biometrics_timeout"
     };
@@ -103,6 +104,7 @@ public class FragmentOptionsPrivacy extends FragmentBase implements SharedPrefer
         swDisplayHidden = view.findViewById(R.id.swDisplayHidden);
         spEncryptMethod = view.findViewById(R.id.spEncryptMethod);
         spOpenPgp = view.findViewById(R.id.spOpenPgp);
+        swAutocryptMutual = view.findViewById(R.id.swAutocryptMutual);
         swSign = view.findViewById(R.id.swSign);
         swEncrypt = view.findViewById(R.id.swEncrypt);
         swAutoDecrypt = view.findViewById(R.id.swAutoDecrypt);
@@ -173,6 +175,13 @@ public class FragmentOptionsPrivacy extends FragmentBase implements SharedPrefer
             }
         });
 
+        swAutocryptMutual.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
+            @Override
+            public void onCheckedChanged(CompoundButton compoundButton, boolean checked) {
+                prefs.edit().putBoolean("autocrypt_mutual", checked).apply();
+            }
+        });
+
         swSign.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
             @Override
             public void onCheckedChanged(CompoundButton compoundButton, boolean checked) {
@@ -347,6 +356,7 @@ public class FragmentOptionsPrivacy extends FragmentBase implements SharedPrefer
                 break;
             }
 
+        swAutocryptMutual.setChecked(prefs.getBoolean("autocrypt_mutual", true));
         swSign.setChecked(prefs.getBoolean("sign_default", false));
         swEncrypt.setChecked(prefs.getBoolean("encrypt_default", false));
         swSign.setEnabled(!swEncrypt.isChecked());
diff --git a/app/src/main/java/eu/faircode/email/MessageHelper.java b/app/src/main/java/eu/faircode/email/MessageHelper.java
index 325210d552..8670b400bc 100644
--- a/app/src/main/java/eu/faircode/email/MessageHelper.java
+++ b/app/src/main/java/eu/faircode/email/MessageHelper.java
@@ -20,10 +20,13 @@ package eu.faircode.email;
 */
 
 import android.content.Context;
+import android.content.SharedPreferences;
 import android.net.MailTo;
 import android.net.Uri;
 import android.text.TextUtils;
 
+import androidx.preference.PreferenceManager;
+
 import com.sun.mail.util.FolderClosedIOException;
 import com.sun.mail.util.MessageRemovedIOException;
 
@@ -233,6 +236,10 @@ public class MessageHelper {
                 if (EntityAttachment.PGP_KEY.equals(attachment.encryption)) {
                     InternetAddress from = (InternetAddress) message.from[0];
 
+                    SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
+                    boolean mutual = prefs.getBoolean("autocrypt_mutual", true);
+                    String mode = (mutual ? "mutual" : "nopreference");
+
                     StringBuilder sb = new StringBuilder();
                     File file = attachment.getFile(context);
                     try (BufferedReader br = new BufferedReader(new FileReader(file))) {
@@ -256,7 +263,7 @@ public class MessageHelper {
                     // https://autocrypt.org/level1.html#the-autocrypt-header
                     imessage.addHeader("Autocrypt",
                             "addr=" + from.getAddress() + ";" +
-                                    " prefer-encrypt=mutual;" +
+                                    " prefer-encrypt=" + mode + ";" +
                                     " keydata=" + sb.toString());
                 }
 
diff --git a/app/src/main/res/layout/fragment_options_privacy.xml b/app/src/main/res/layout/fragment_options_privacy.xml
index b467b08673..eb77f18e29 100644
--- a/app/src/main/res/layout/fragment_options_privacy.xml
+++ b/app/src/main/res/layout/fragment_options_privacy.xml
@@ -102,6 +102,18 @@
             app:layout_constraintStart_toStartOf="parent"
             app:layout_constraintTop_toBottomOf="@id/tvOpenPgp" />
 
+        <androidx.appcompat.widget.SwitchCompat
+            android:id="@+id/swAutocryptMutual"
+            android:layout_width="0dp"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="12dp"
+            android:checked="true"
+            android:text="@string/title_advanced_autocrypt_mutual"
+            app:layout_constraintEnd_toEndOf="parent"
+            app:layout_constraintStart_toStartOf="parent"
+            app:layout_constraintTop_toBottomOf="@id/spOpenPgp"
+            app:switchPadding="12dp" />
+
         <androidx.appcompat.widget.SwitchCompat
             android:id="@+id/swSign"
             android:layout_width="0dp"
@@ -110,7 +122,7 @@
             android:text="@string/title_advanced_sign_default"
             app:layout_constraintEnd_toEndOf="parent"
             app:layout_constraintStart_toStartOf="parent"
-            app:layout_constraintTop_toBottomOf="@id/spOpenPgp"
+            app:layout_constraintTop_toBottomOf="@id/swAutocryptMutual"
             app:switchPadding="12dp" />
 
         <androidx.appcompat.widget.SwitchCompat
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index 32e7564b61..d5dbd36c73 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -340,6 +340,7 @@
     <string name="title_advanced_display_hidden">Display hidden message texts</string>
     <string name="title_advanced_encrypt_method">Default encryption method</string>
     <string name="title_advanced_openpgp">OpenPGP provider</string>
+    <string name="title_advanced_autocrypt_mutual">Autocrypt mutual mode</string>
     <string name="title_advanced_sign_default">Sign by default</string>
     <string name="title_advanced_encrypt_default">Encrypt by default</string>
     <string name="title_advanced_auto_decrypt">Automatically decrypt messages</string>