diff --git a/app/src/main/java/eu/faircode/email/EmailService.java b/app/src/main/java/eu/faircode/email/EmailService.java
index ec61ef7322..9d63c73032 100644
--- a/app/src/main/java/eu/faircode/email/EmailService.java
+++ b/app/src/main/java/eu/faircode/email/EmailService.java
@@ -179,8 +179,13 @@ public class EmailService implements AutoCloseable {
 
         boolean auth_plain = prefs.getBoolean("auth_plain", true);
         boolean auth_login = prefs.getBoolean("auth_login", true);
+        boolean auth_ntlm = prefs.getBoolean("auth_ntlm", true);
         boolean auth_sasl = prefs.getBoolean("auth_sasl", true);
-        Log.i("Authenticate plain=" + auth_plain + " login=" + auth_login + " sasl=" + auth_sasl);
+        Log.i("Authenticate" +
+                " plain=" + auth_plain +
+                " login=" + auth_login +
+                " ntlm=" + auth_ntlm +
+                " sasl=" + auth_sasl);
 
         properties.put("mail.event.scope", "folder");
         properties.put("mail.event.executor", executor);
@@ -189,6 +194,8 @@ public class EmailService implements AutoCloseable {
             properties.put("mail." + protocol + ".auth.plain.disable", "true");
         if (!auth_login)
             properties.put("mail." + protocol + ".auth.login.disable", "true");
+        if (!auth_ntlm)
+            properties.put("mail." + protocol + ".auth.ntlm.disable", "true");
 
         // SASL is attempted before other authentication methods
         properties.put("mail." + protocol + ".sasl.enable", Boolean.toString(auth_sasl));
diff --git a/app/src/main/java/eu/faircode/email/FragmentOptionsMisc.java b/app/src/main/java/eu/faircode/email/FragmentOptionsMisc.java
index 84b9b55a44..3f28efb659 100644
--- a/app/src/main/java/eu/faircode/email/FragmentOptionsMisc.java
+++ b/app/src/main/java/eu/faircode/email/FragmentOptionsMisc.java
@@ -111,6 +111,7 @@ public class FragmentOptionsMisc extends FragmentBase implements SharedPreferenc
     private SwitchCompat swDebug;
     private SwitchCompat swAuthPlain;
     private SwitchCompat swAuthLogin;
+    private SwitchCompat swAuthNtlm;
     private SwitchCompat swAuthSasl;
     private TextView tvProcessors;
     private TextView tvMemoryClass;
@@ -132,7 +133,7 @@ public class FragmentOptionsMisc extends FragmentBase implements SharedPreferenc
             "classification", "class_min_probability", "class_min_difference",
             "language", "watchdog", "updates",
             "experiments", "query_threads", "crash_reports", "cleanup_attachments",
-            "protocol", "debug", "auth_plain", "auth_login", "auth_sasl"
+            "protocol", "debug", "auth_plain", "auth_login", "auth_ntlm", "auth_sasl"
     };
 
     private final static String[] RESET_QUESTIONS = new String[]{
@@ -201,6 +202,7 @@ public class FragmentOptionsMisc extends FragmentBase implements SharedPreferenc
         swDebug = view.findViewById(R.id.swDebug);
         swAuthPlain = view.findViewById(R.id.swAuthPlain);
         swAuthLogin = view.findViewById(R.id.swAuthLogin);
+        swAuthNtlm = view.findViewById(R.id.swAuthNtlm);
         swAuthSasl = view.findViewById(R.id.swAuthSasl);
         tvProcessors = view.findViewById(R.id.tvProcessors);
         tvMemoryClass = view.findViewById(R.id.tvMemoryClass);
@@ -481,6 +483,13 @@ public class FragmentOptionsMisc extends FragmentBase implements SharedPreferenc
             }
         });
 
+        swAuthNtlm.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
+            @Override
+            public void onCheckedChanged(CompoundButton compoundButton, boolean checked) {
+                prefs.edit().putBoolean("auth_ntlm", checked).apply();
+            }
+        });
+
         swAuthSasl.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
             @Override
             public void onCheckedChanged(CompoundButton compoundButton, boolean checked) {
@@ -840,6 +849,7 @@ public class FragmentOptionsMisc extends FragmentBase implements SharedPreferenc
         swDebug.setChecked(prefs.getBoolean("debug", false));
         swAuthPlain.setChecked(prefs.getBoolean("auth_plain", true));
         swAuthLogin.setChecked(prefs.getBoolean("auth_login", true));
+        swAuthNtlm.setChecked(prefs.getBoolean("auth_ntlm", true));
         swAuthSasl.setChecked(prefs.getBoolean("auth_sasl", true));
 
         tvProcessors.setText(getString(R.string.title_advanced_processors, Runtime.getRuntime().availableProcessors()));
diff --git a/app/src/main/java/eu/faircode/email/ServiceSynchronize.java b/app/src/main/java/eu/faircode/email/ServiceSynchronize.java
index c7a557177b..30b8c83d5e 100644
--- a/app/src/main/java/eu/faircode/email/ServiceSynchronize.java
+++ b/app/src/main/java/eu/faircode/email/ServiceSynchronize.java
@@ -148,9 +148,7 @@ public class ServiceSynchronize extends ServiceBase implements SharedPreferences
             "prefer_ip4", "standalone_vpn", "tcp_keep_alive", "ssl_harden", // force reconnect
             "badge", "unseen_ignored", // force update badge/widget
             "experiments", "debug", "protocol", // force reconnect
-            "auth_plain",
-            "auth_login",
-            "auth_sasl"
+            "auth_plain", "auth_login", "auth_ntlm", "auth_sasl" // force reconnect
     ));
 
     static final int PI_ALARM = 1;
diff --git a/app/src/main/res/layout/fragment_options_misc.xml b/app/src/main/res/layout/fragment_options_misc.xml
index c0bf16c6ad..797ece635f 100644
--- a/app/src/main/res/layout/fragment_options_misc.xml
+++ b/app/src/main/res/layout/fragment_options_misc.xml
@@ -504,6 +504,18 @@
             app:layout_constraintTop_toBottomOf="@id/swAuthPlain"
             app:switchPadding="12dp" />
 
+        <androidx.appcompat.widget.SwitchCompat
+            android:id="@+id/swAuthNtlm"
+            android:layout_width="0dp"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="12dp"
+            android:checked="true"
+            android:text="@string/title_advanced_auth_ntlm"
+            app:layout_constraintEnd_toEndOf="parent"
+            app:layout_constraintStart_toStartOf="parent"
+            app:layout_constraintTop_toBottomOf="@id/swAuthLogin"
+            app:switchPadding="12dp" />
+
         <androidx.appcompat.widget.SwitchCompat
             android:id="@+id/swAuthSasl"
             android:layout_width="0dp"
@@ -513,7 +525,7 @@
             android:text="@string/title_advanced_auth_sasl"
             app:layout_constraintEnd_toEndOf="parent"
             app:layout_constraintStart_toStartOf="parent"
-            app:layout_constraintTop_toBottomOf="@id/swAuthLogin"
+            app:layout_constraintTop_toBottomOf="@id/swAuthNtlm"
             app:switchPadding="12dp" />
 
         <eu.faircode.email.FixedTextView
@@ -603,6 +615,6 @@
             android:id="@+id/grpDebug"
             android:layout_width="0dp"
             android:layout_height="0dp"
-            app:constraint_referenced_ids="swAuthPlain,swAuthLogin,swAuthSasl,tvProcessors,tvMemoryClass,tvMemoryUsage,tvStorageUsage,tvFingerprint,btnCharsets,btnCiphers,btnFiles" />
+            app:constraint_referenced_ids="swAuthPlain,swAuthLogin,swAuthNtlm,swAuthSasl,tvProcessors,tvMemoryClass,tvMemoryUsage,tvStorageUsage,tvFingerprint,btnCharsets,btnCiphers,btnFiles" />
     </androidx.constraintlayout.widget.ConstraintLayout>
 </eu.faircode.email.ScrollViewEx>
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index 7440db97ef..8ca567e9f3 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -527,6 +527,7 @@
     <string name="title_advanced_watchdog">Periodically check if FairEmail is still active</string>
     <string name="title_advanced_auth_plain" translatable="false">PLAIN</string>
     <string name="title_advanced_auth_login" translatable="false">LOGIN</string>
+    <string name="title_advanced_auth_ntlm" translatable="false">NTLM</string>
     <string name="title_advanced_auth_sasl" translatable="false">SASL</string>
     <string name="title_advanced_optimize">Automatically optimize</string>
     <string name="title_advanced_updates">Check for GitHub updates</string>