diff --git a/src/app/Http/Controllers/API/V4/NGINXController.php b/src/app/Http/Controllers/API/V4/NGINXController.php
--- a/src/app/Http/Controllers/API/V4/NGINXController.php
+++ b/src/app/Http/Controllers/API/V4/NGINXController.php
@@ -193,7 +193,7 @@
         // All checks passed
         switch ($request->headers->get('Auth-Protocol')) {
             case "imap":
-                return $this->authenticateIMAP($request, $user->getSetting('guam_enabled', false), $password);
+                return $this->authenticateIMAP($request, (bool) $user->getSetting('guam_enabled'), $password);
             case "smtp":
                 return $this->authenticateSMTP($request, $password);
             default:
diff --git a/src/app/Traits/UserConfigTrait.php b/src/app/Traits/UserConfigTrait.php
--- a/src/app/Traits/UserConfigTrait.php
+++ b/src/app/Traits/UserConfigTrait.php
@@ -11,10 +11,17 @@
      */
     public function getConfig(): array
     {
-        $settings = $this->getSettings(['greylist_enabled', 'password_policy', 'max_password_age', 'limit_geo']);
+        $settings = $this->getSettings([
+                'greylist_enabled',
+                'guam_enabled',
+                'password_policy',
+                'max_password_age',
+                'limit_geo'
+        ]);
 
         $config = [
             'greylist_enabled' => $settings['greylist_enabled'] !== 'false',
+            'guam_enabled' => $settings['guam_enabled'] === 'true',
             'limit_geo' => $settings['limit_geo'] ? json_decode($settings['limit_geo'], true) : [],
             'max_password_age' => $settings['max_password_age'],
             'password_policy' => $settings['password_policy'],
@@ -37,6 +44,8 @@
         foreach ($config as $key => $value) {
             if ($key == 'greylist_enabled') {
                 $this->setSetting($key, $value ? 'true' : 'false');
+            } elseif ($key == 'guam_enabled') {
+                $this->setSetting($key, $value ? 'true' : null);
             } elseif ($key == 'limit_geo') {
                 if (!is_array($value)) {
                     $errors[$key] = \trans('validation.invalid-limit-geo');
diff --git a/src/resources/lang/en/ui.php b/src/resources/lang/en/ui.php
--- a/src/resources/lang/en/ui.php
+++ b/src/resources/lang/en/ui.php
@@ -461,6 +461,8 @@
         'greylisting-text' => "Greylisting is a method of defending users against spam. Any incoming mail from an unrecognized sender "
             . "is temporarily rejected. The originating server should try again after a delay. "
             . "This time the email will be accepted. Spammers usually do not reattempt mail delivery.",
+        'imapproxy' => "IMAP proxy",
+        'imapproxy-text' => "Enables IMAP proxy that filters out non-mail groupware folders, so your IMAP clients do not see them.",
         'list-title' => "User accounts",
         'list-empty' => "There are no users in this account.",
         'managed-by' => "Managed by",
diff --git a/src/resources/vue/Admin/User.vue b/src/resources/vue/Admin/User.vue
--- a/src/resources/vue/Admin/User.vue
+++ b/src/resources/vue/Admin/User.vue
@@ -206,6 +206,15 @@
                                 </div>
                             </div>
                             <div class="row plaintext">
+                                <label for="guam_enabled" class="col-sm-4 col-form-label">{{ $t('user.imapproxy') }}</label>
+                                <div class="col-sm-8">
+                                    <span class="form-control-plaintext" id="guam_enabled">
+                                        <span v-if="user.config.guam_enabled" class="text-success">{{ $t('form.enabled') }}</span>
+                                        <span v-else class="text-danger">{{ $t('form.disabled') }}</span>
+                                    </span>
+                                </div>
+                            </div>
+                            <div class="row plaintext">
                                 <label for="limit_geo" class="col-sm-4 col-form-label">{{ $t('user.geolimit') }}</label>
                                 <div class="col-sm-8">
                                     <span class="form-control-plaintext" id="limit_geo">
diff --git a/src/resources/vue/User/Info.vue b/src/resources/vue/User/Info.vue
--- a/src/resources/vue/User/Info.vue
+++ b/src/resources/vue/User/Info.vue
@@ -93,6 +93,18 @@
                                         </small>
                                     </div>
                                 </div>
+                                <div v-if="$root.hasPermission('beta')" class="row checkbox mb-3">
+                                    <label for="guam_enabled" class="col-sm-4 col-form-label">
+                                        {{ $t('user.imapproxy') }}
+                                        <sup class="badge bg-primary">{{ $t('dashboard.beta') }}</sup>
+                                    </label>
+                                    <div class="col-sm-8 pt-2">
+                                        <input type="checkbox" id="guam_enabled" name="guam_enabled" value="1" class="form-check-input d-block mb-2" :checked="user.config.guam_enabled">
+                                        <small id="guam-hint" class="text-muted">
+                                            {{ $t('user.imapproxy-text') }}
+                                        </small>
+                                    </div>
+                                </div>
                                 <div v-if="$root.hasPermission('beta')" class="row mb-3">
                                     <label for="limit_geo" class="col-sm-4 col-form-label">
                                         {{ $t('user.geolimit') }}
@@ -272,7 +284,12 @@
 
                 let post = this.$root.pick(this.user.config, ['limit_geo'])
 
-                post.greylist_enabled = $('#greylist_enabled').prop('checked') ? 1 : 0
+                const checklist = ['greylist_enabled', 'guam_enabled']
+                checklist.forEach(name => {
+                    if ($('#' + name).length) {
+                        post[name] = $('#' + name).prop('checked') ? 1 : 0
+                    }
+                })
 
                 axios.post('/api/v4/users/' + this.user_id + '/config', post)
                     .then(response => {
diff --git a/src/tests/Browser/Admin/UserTest.php b/src/tests/Browser/Admin/UserTest.php
--- a/src/tests/Browser/Admin/UserTest.php
+++ b/src/tests/Browser/Admin/UserTest.php
@@ -87,6 +87,7 @@
         $this->browse(function (Browser $browser) {
             $jack = $this->getTestUser('jack@kolab.org');
             $jack->setSetting('limit_geo', null);
+            $jack->setSetting('guam_enabled', null);
 
             $page = new UserPage($jack->id);
 
@@ -191,11 +192,13 @@
             $browser->assertSeeIn('@nav #tab-settings', 'Settings')
                 ->click('@nav #tab-settings')
                 ->whenAvailable('@user-settings form', function (Browser $browser) {
-                    $browser->assertElementsCount('.row', 2)
+                    $browser->assertElementsCount('.row', 3)
                         ->assertSeeIn('.row:first-child label', 'Greylisting')
                         ->assertSeeIn('.row:first-child .text-success', 'enabled')
-                        ->assertSeeIn('.row:nth-child(2) label', 'Geo-lockin')
-                        ->assertSeeIn('.row:nth-child(2) #limit_geo', 'No restrictions')
+                        ->assertSeeIn('.row:nth-child(2) label', 'IMAP proxy')
+                        ->assertSeeIn('.row:nth-child(2) .text-danger', 'disabled')
+                        ->assertSeeIn('.row:nth-child(3) label', 'Geo-lockin')
+                        ->assertSeeIn('.row:nth-child(3) #limit_geo', 'No restrictions')
                         ->assertMissing('#limit_geo + button');
                 });
         });
@@ -465,7 +468,7 @@
             $browser->assertSeeIn('@nav #tab-settings', 'Settings')
                 ->click('@nav #tab-settings')
                 ->whenAvailable('@user-settings form', function (Browser $browser) {
-                    $browser->assertElementsCount('.row', 2)
+                    $browser->assertElementsCount('.row', 3)
                         ->assertSeeIn('.row:first-child label', 'Greylisting')
                         ->assertSeeIn('.row:first-child .text-danger', 'disabled');
                 });
@@ -593,8 +596,8 @@
             $browser->visit(new UserPage($user->id))
                 ->click('@nav #tab-settings')
                 ->whenAvailable('@user-settings form', function (Browser $browser) {
-                    $browser->assertSeeIn('.row:nth-child(2) label', 'Geo-lockin')
-                        ->assertSeeIn('.row:nth-child(2) #limit_geo', 'Poland, Germany')
+                    $browser->assertSeeIn('.row:nth-child(3) label', 'Geo-lockin')
+                        ->assertSeeIn('.row:nth-child(3) #limit_geo', 'Poland, Germany')
                         ->assertSeeIn('#limit_geo + button', 'Reset')
                         ->click('#limit_geo + button');
                 })
diff --git a/src/tests/Browser/UsersTest.php b/src/tests/Browser/UsersTest.php
--- a/src/tests/Browser/UsersTest.php
+++ b/src/tests/Browser/UsersTest.php
@@ -27,6 +27,7 @@
         'first_name' => 'John',
         'last_name' => 'Doe',
         'organization' => 'Kolab Developers',
+        'limit_geo' => null,
     ];
 
     /**
@@ -362,6 +363,7 @@
     {
         $john = $this->getTestUser('john@kolab.org');
         $john->setSetting('greylist_enabled', null);
+        $john->setSetting('guam_enabled', null);
         $john->setSetting('limit_geo', null);
 
         $this->browse(function (Browser $browser) use ($john) {
@@ -373,7 +375,7 @@
                 ->click('@nav #tab-settings')
                 ->with('#settings form', function (Browser $browser) {
                     $browser->assertSeeIn('div.row:nth-child(1) label', 'Greylisting')
-                        ->assertMissing('div.row:nth-child(2)') // geo-lockin setting is hidden
+                        ->assertMissing('div.row:nth-child(2)') // guam and geo-lockin settings are hidden
                         ->click('div.row:nth-child(1) input[type=checkbox]:checked')
                         ->click('button[type=submit]')
                         ->assertToast(Toast::TYPE_SUCCESS, 'User settings updated successfully.');
@@ -390,26 +392,32 @@
                 ->click('@nav #tab-settings')
                 ->with('#settings form', function (Browser $browser) use ($john) {
                     $browser->assertSeeIn('div.row:nth-child(1) label', 'Greylisting')
-                        ->assertSeeIn('div.row:nth-child(2) label', 'Geo-lockin')
+                        ->assertSeeIn('div.row:nth-child(2) label', 'IMAP proxy')
+                        ->assertNotChecked('div.row:nth-child(2) input')
+                        ->assertSeeIn('div.row:nth-child(3) label', 'Geo-lockin')
                         ->with(new CountrySelect('#limit_geo'), function ($browser) {
                             $browser->assertCountries([])
                                 ->setCountries(['DE', 'PL'])
                                 ->assertCountries(['DE', 'PL']);
                         })
+                        ->click('div.row:nth-child(2) input')
                         ->click('button[type=submit]')
                         ->assertToast(Toast::TYPE_SUCCESS, 'User settings updated successfully.');
 
                     $this->assertSame('["DE","PL"]', $john->getSetting('limit_geo'));
+                    $this->assertSame('true', $john->getSetting('guam_enabled'));
 
                     $browser
                         ->with(new CountrySelect('#limit_geo'), function ($browser) {
                             $browser->setCountries([])
                                 ->assertCountries([]);
                         })
+                        ->click('div.row:nth-child(2) input')
                         ->click('button[type=submit]')
                         ->assertToast(Toast::TYPE_SUCCESS, 'User settings updated successfully.');
 
                     $this->assertSame(null, $john->getSetting('limit_geo'));
+                    $this->assertSame(null, $john->getSetting('guam_enabled'));
                 });
         });
     }
diff --git a/src/tests/Feature/Controller/NGINXTest.php b/src/tests/Feature/Controller/NGINXTest.php
--- a/src/tests/Feature/Controller/NGINXTest.php
+++ b/src/tests/Feature/Controller/NGINXTest.php
@@ -18,7 +18,7 @@
         \App\AuthAttempt::where('user_id', $john->id)->delete();
         $john->setSettings([
                 'limit_geo' => null,
-                'guam_enabled' => false,
+                'guam_enabled' => null,
         ]);
         \App\IP4Net::where('net_number', inet_pton('127.0.0.0'))->delete();
 
@@ -35,7 +35,7 @@
         \App\AuthAttempt::where('user_id', $john->id)->delete();
         $john->setSettings([
                 'limit_geo' => null,
-                'guam_enabled' => false,
+                'guam_enabled' => null,
         ]);
         \App\IP4Net::where('net_number', inet_pton('127.0.0.0'))->delete();
 
@@ -131,7 +131,7 @@
 
 
         // Guam
-        $john->setSettings(['guam_enabled' => true]);
+        $john->setSettings(['guam_enabled' => 'true']);
 
         $response = $this->withHeaders($headers)->get("api/webhooks/nginx");
         $response->assertStatus(200);
diff --git a/src/tests/Feature/Controller/UsersTest.php b/src/tests/Feature/Controller/UsersTest.php
--- a/src/tests/Feature/Controller/UsersTest.php
+++ b/src/tests/Feature/Controller/UsersTest.php
@@ -45,6 +45,7 @@
         $wallet->discount()->dissociate();
         $wallet->settings()->whereIn('key', ['mollie_id', 'stripe_id'])->delete();
         $wallet->save();
+        $user->settings()->whereIn('key', ['greylist_enabled', 'guam_enabled'])->delete();
         $user->status |= User::STATUS_IMAP_READY;
         $user->save();
     }
@@ -75,7 +76,7 @@
         $wallet->discount()->dissociate();
         $wallet->settings()->whereIn('key', ['mollie_id', 'stripe_id'])->delete();
         $wallet->save();
-        $user->settings()->whereIn('key', ['greylist_enabled'])->delete();
+        $user->settings()->whereIn('key', ['greylist_enabled', 'guam_enabled'])->delete();
         $user->status |= User::STATUS_IMAP_READY;
         $user->save();
 
@@ -297,6 +298,7 @@
         $this->assertTrue(is_array($json['statusInfo']));
         $this->assertTrue(is_array($json['settings']));
         $this->assertTrue($json['config']['greylist_enabled']);
+        $this->assertFalse($json['config']['guam_enabled']);
         $this->assertSame([], $json['skus']);
         $this->assertSame([], $json['aliases']);
         // Values below are tested by Unit tests
@@ -647,6 +649,7 @@
         $john = $this->getTestUser('john@kolab.org');
 
         $john->setSetting('greylist_enabled', null);
+        $john->setSetting('guam_enabled', null);
         $john->setSetting('password_policy', null);
         $john->setSetting('max_password_age', null);
 
@@ -686,6 +689,7 @@
         // Test some valid data
         $post = [
             'greylist_enabled' => 1,
+            'guam_enabled' => 1,
             'password_policy' => 'min:10,max:255,upper,lower,digit,special',
             'max_password_age' => 6,
         ];
@@ -700,12 +704,13 @@
         $this->assertSame('User settings updated successfully.', $json['message']);
 
         $this->assertSame('true', $john->getSetting('greylist_enabled'));
+        $this->assertSame('true', $john->getSetting('guam_enabled'));
         $this->assertSame('min:10,max:255,upper,lower,digit,special', $john->getSetting('password_policy'));
         $this->assertSame('6', $john->getSetting('max_password_age'));
 
         // Test some valid data, acting as another account controller
         $ned = $this->getTestUser('ned@kolab.org');
-        $post = ['greylist_enabled' => 0, 'password_policy' => 'min:10,max:255,upper,last:1'];
+        $post = ['greylist_enabled' => 0, 'guam_enabled' => 0, 'password_policy' => 'min:10,max:255,upper,last:1'];
         $response = $this->actingAs($ned)->post("/api/v4/users/{$john->id}/config", $post);
         $response->assertStatus(200);
 
@@ -716,6 +721,7 @@
         $this->assertSame('User settings updated successfully.', $json['message']);
 
         $this->assertSame('false', $john->fresh()->getSetting('greylist_enabled'));
+        $this->assertSame(null, $john->fresh()->getSetting('guam_enabled'));
         $this->assertSame('min:10,max:255,upper,last:1', $john->fresh()->getSetting('password_policy'));
     }
 
diff --git a/src/tests/Feature/UserTest.php b/src/tests/Feature/UserTest.php
--- a/src/tests/Feature/UserTest.php
+++ b/src/tests/Feature/UserTest.php
@@ -468,6 +468,7 @@
     {
         $user = $this->getTestUser('UserAccountA@UserAccount.com');
         $user->setSetting('greylist_enabled', null);
+        $user->setSetting('guam_enabled', null);
         $user->setSetting('password_policy', null);
         $user->setSetting('max_password_age', null);
         $user->setSetting('limit_geo', null);
@@ -487,6 +488,21 @@
         $this->assertSame(true, $user->getConfig()['greylist_enabled']);
         $this->assertSame('true', $user->getSetting('greylist_enabled'));
 
+        // guam_enabled
+        $this->assertSame(false, $user->getConfig()['guam_enabled']);
+
+        $result = $user->setConfig(['guam_enabled' => false]);
+
+        $this->assertSame([], $result);
+        $this->assertSame(false, $user->getConfig()['guam_enabled']);
+        $this->assertSame(null, $user->getSetting('guam_enabled'));
+
+        $result = $user->setConfig(['guam_enabled' => true]);
+
+        $this->assertSame([], $result);
+        $this->assertSame(true, $user->getConfig()['guam_enabled']);
+        $this->assertSame('true', $user->getSetting('guam_enabled'));
+
         // max_apssword_age
         $this->assertSame(null, $user->getConfig()['max_password_age']);