diff --git a/api/modules/authserver/Module.php b/api/modules/authserver/Module.php
index b2c1b22..09e0026 100644
--- a/api/modules/authserver/Module.php
+++ b/api/modules/authserver/Module.php
@@ -6,6 +6,7 @@ namespace api\modules\authserver;
 use Yii;
 use yii\base\BootstrapInterface;
 use yii\web\NotFoundHttpException;
+use yii\web\Response;
 
 class Module extends \yii\base\Module implements BootstrapInterface {
 
@@ -13,7 +14,7 @@ class Module extends \yii\base\Module implements BootstrapInterface {
 
     public $defaultRoute = 'index';
 
-    public function beforeAction($action) {
+    public function beforeAction($action): bool {
         if (!parent::beforeAction($action)) {
             return false;
         }
@@ -23,10 +24,18 @@ class Module extends \yii\base\Module implements BootstrapInterface {
         return true;
     }
 
+    public function afterAction($action, $result) {
+        if ($result === null) {
+            Yii::$app->response->format = Response::FORMAT_RAW;
+        }
+
+        return parent::afterAction($action, $result);
+    }
+
     /**
      * @param \yii\base\Application $app
      */
-    public function bootstrap($app) {
+    public function bootstrap($app): void {
         $legacyHost = $app->params['authserverHost'];
         $app->getUrlManager()->addRules([
             "//{$legacyHost}/authserver/auth/<action>" => "{$this->id}/authentication/<action>",
diff --git a/api/tests/functional/authserver/InvalidateCest.php b/api/tests/functional/authserver/InvalidateCest.php
index 46db699..ad1506a 100644
--- a/api/tests/functional/authserver/InvalidateCest.php
+++ b/api/tests/functional/authserver/InvalidateCest.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace api\tests\functional\authserver;
 
 use api\tests\_pages\AuthserverRoute;
diff --git a/api/tests/unit/models/authentication/RegistrationFormTest.php b/api/tests/unit/models/authentication/RegistrationFormTest.php
index c1a7184..cc61563 100644
--- a/api/tests/unit/models/authentication/RegistrationFormTest.php
+++ b/api/tests/unit/models/authentication/RegistrationFormTest.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace api\tests\_support\models\authentication;
 
 use api\components\ReCaptcha\Validator as ReCaptchaValidator;
@@ -55,7 +57,8 @@ class RegistrationFormTest extends TestCase {
     }
 
     public function testSignup() {
-        Mock::func(EmailValidator::class, 'checkdnsrr')->andReturnTrue();
+        Mock::func(EmailValidator::class, 'checkdnsrr')->andReturn(true);
+        Mock::func(EmailValidator::class, 'dns_get_record')->andReturn(['']);
         $model = new RegistrationForm([
             'username' => 'some_username',
             'email' => 'some_email@example.com',
@@ -72,7 +75,8 @@ class RegistrationFormTest extends TestCase {
     }
 
     public function testSignupWithDefaultLanguage() {
-        Mock::func(EmailValidator::class, 'checkdnsrr')->andReturnTrue();
+        Mock::func(EmailValidator::class, 'checkdnsrr')->andReturn(true);
+        Mock::func(EmailValidator::class, 'dns_get_record')->andReturn(['']);
         $model = new RegistrationForm([
             'username' => 'some_username',
             'email' => 'some_email@example.com',
diff --git a/common/tests/helpers/Mock.php b/common/tests/helpers/Mock.php
index 78fe5ab..75eb57e 100644
--- a/common/tests/helpers/Mock.php
+++ b/common/tests/helpers/Mock.php
@@ -1,5 +1,6 @@
 <?php
 declare(strict_types=1);
+
 namespace common\tests\helpers;
 
 use phpmock\mockery\PHPMockery;
@@ -17,6 +18,10 @@ class Mock {
         return PHPMockery::mock(self::getClassNamespace($className), $function);
     }
 
+    public static function define(string $className, string $function): void {
+        PHPMockery::define(self::getClassNamespace($className), $function);
+    }
+
     private static function getClassNamespace(string $className): string {
         return (new ReflectionClass($className))->getNamespaceName();
     }
diff --git a/common/tests/unit/validators/EmailValidatorTest.php b/common/tests/unit/validators/EmailValidatorTest.php
index 711c2d8..778a37b 100644
--- a/common/tests/unit/validators/EmailValidatorTest.php
+++ b/common/tests/unit/validators/EmailValidatorTest.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace common\tests\unit\validators;
 
 use common\tests\fixtures\AccountFixture;
@@ -17,6 +19,10 @@ class EmailValidatorTest extends TestCase {
 
     public function _before() {
         parent::_before();
+
+        Mock::define(YiiEmailValidator::class, 'checkdnsrr');
+        Mock::define(YiiEmailValidator::class, 'dns_get_record');
+
         $this->validator = new EmailValidator();
     }
 
@@ -41,7 +47,8 @@ class EmailValidatorTest extends TestCase {
     }
 
     public function testValidateAttributeLength() {
-        Mock::func(YiiEmailValidator::class, 'checkdnsrr')->andReturnTrue();
+        Mock::func(YiiEmailValidator::class, 'checkdnsrr')->andReturn(false);
+
         $model = $this->createModel(
             'emailemailemailemailemailemailemailemailemailemailemailemailemailemailemailemailemail' .
             'emailemailemailemailemailemailemailemailemailemailemailemailemailemailemailemailemail' .
@@ -56,16 +63,27 @@ class EmailValidatorTest extends TestCase {
         $this->assertNotSame(['error.email_too_long'], $model->getErrors('field'));
     }
 
-    public function testValidateAttributeEmail() {
-        Mock::func(YiiEmailValidator::class, 'checkdnsrr')->times(3)->andReturnValues([false, false, true]);
+    public function testValidateAttributeEmailCaseNotExistsDomain() {
+        Mock::func(YiiEmailValidator::class, 'checkdnsrr')->andReturn(false);
+        Mock::func(YiiEmailValidator::class, 'dns_get_record')->times(0);
 
-        $model = $this->createModel('non-email');
+        $model = $this->createModel('non-email@this-domain-does-not-exists.de');
         $this->validator->validateAttribute($model, 'field');
         $this->assertSame(['error.email_invalid'], $model->getErrors('field'));
+    }
 
-        $model = $this->createModel('non-email@etot-domen-ne-suschestrvyet.de');
+    public function testValidateAttributeEmailCaseExistsDomainButWithoutMXRecord() {
+        Mock::func(YiiEmailValidator::class, 'checkdnsrr')->andReturnValues([false, true]);
+        Mock::func(YiiEmailValidator::class, 'dns_get_record')->andReturn(['127.0.0.1']);
+
+        $model = $this->createModel('non-email@this-domain-has-no-mx-record.de');
         $this->validator->validateAttribute($model, 'field');
-        $this->assertSame(['error.email_invalid'], $model->getErrors('field'));
+        $this->assertNotSame(['error.email_invalid'], $model->getErrors('field'));
+    }
+
+    public function testValidateAttributeEmailCaseExistsDomainWithMXRecord() {
+        Mock::func(YiiEmailValidator::class, 'checkdnsrr')->andReturn(true);
+        Mock::func(YiiEmailValidator::class, 'dns_get_record')->andReturn(['mx.google.com']);
 
         $model = $this->createModel('valid-email@gmail.com');
         $this->validator->validateAttribute($model, 'field');
@@ -73,7 +91,8 @@ class EmailValidatorTest extends TestCase {
     }
 
     public function testValidateAttributeTempmail() {
-        Mock::func(YiiEmailValidator::class, 'checkdnsrr')->times(2)->andReturnTrue();
+        Mock::func(YiiEmailValidator::class, 'checkdnsrr')->andReturn(true);
+        Mock::func(YiiEmailValidator::class, 'dns_get_record')->andReturn(['127.0.0.1']);
 
         $model = $this->createModel('ibrpycwyjdnt@dropmail.me');
         $this->validator->validateAttribute($model, 'field');
@@ -85,7 +104,8 @@ class EmailValidatorTest extends TestCase {
     }
 
     public function testValidateAttributeIdna() {
-        Mock::func(YiiEmailValidator::class, 'checkdnsrr')->times(2)->andReturnTrue();
+        Mock::func(YiiEmailValidator::class, 'checkdnsrr')->andReturn(true);
+        Mock::func(YiiEmailValidator::class, 'dns_get_record')->andReturn(['127.0.0.1']);
 
         $model = $this->createModel('qdushyantasunassm@❕.gq');
         $this->validator->validateAttribute($model, 'field');
@@ -97,7 +117,8 @@ class EmailValidatorTest extends TestCase {
     }
 
     public function testValidateAttributeUnique() {
-        Mock::func(YiiEmailValidator::class, 'checkdnsrr')->times(3)->andReturnTrue();
+        Mock::func(YiiEmailValidator::class, 'checkdnsrr')->andReturn(true);
+        Mock::func(YiiEmailValidator::class, 'dns_get_record')->andReturn(['127.0.0.1']);
 
         $this->tester->haveFixtures([
             'accounts' => AccountFixture::class,
diff --git a/composer.json b/composer.json
index f39482e..864979b 100644
--- a/composer.json
+++ b/composer.json
@@ -6,6 +6,7 @@
     "minimum-stability": "stable",
     "require": {
         "php": "^7.2",
+        "ext-intl": "*",
         "ext-json": "*",
         "ext-libxml": "*",
         "ext-mbstring": "*",
@@ -24,7 +25,7 @@
         "ramsey/uuid": "^3.5",
         "spomky-labs/otphp": "^9.0.2",
         "webmozart/assert": "^1.2.0",
-        "yiisoft/yii2": "2.0.15.1",
+        "yiisoft/yii2": "~2.0.20",
         "yiisoft/yii2-queue": "^2.2.0",
         "yiisoft/yii2-redis": "~2.0.0",
         "yiisoft/yii2-swiftmailer": "~2.1.0"
diff --git a/composer.lock b/composer.lock
index d6056bc..7a3d699 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "752322170e3433ba42cb90c1dd6122a2",
+    "content-hash": "80ccf8b828493911307a9daa95021dfc",
     "packages": [
         {
             "name": "bacon/bacon-qr-code",
@@ -1988,24 +1988,24 @@
         },
         {
             "name": "yiisoft/yii2",
-            "version": "2.0.15.1",
+            "version": "2.0.20",
             "source": {
                 "type": "git",
                 "url": "https://github.com/yiisoft/yii2-framework.git",
-                "reference": "ed3a9e1c4abe206e1c3ce48a6b3624119b79850d"
+                "reference": "bd05e0e0ac353cb239997da78f459d0960a1fe9f"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/yiisoft/yii2-framework/zipball/ed3a9e1c4abe206e1c3ce48a6b3624119b79850d",
-                "reference": "ed3a9e1c4abe206e1c3ce48a6b3624119b79850d",
+                "url": "https://api.github.com/repos/yiisoft/yii2-framework/zipball/bd05e0e0ac353cb239997da78f459d0960a1fe9f",
+                "reference": "bd05e0e0ac353cb239997da78f459d0960a1fe9f",
                 "shasum": ""
             },
             "require": {
                 "bower-asset/inputmask": "~3.2.2 | ~3.3.5",
-                "bower-asset/jquery": "3.2.*@stable | 3.1.*@stable | 2.2.*@stable | 2.1.*@stable | 1.11.*@stable | 1.12.*@stable",
+                "bower-asset/jquery": "3.4.*@stable | 3.3.*@stable | 3.2.*@stable | 3.1.*@stable | 2.2.*@stable | 2.1.*@stable | 1.11.*@stable | 1.12.*@stable",
                 "bower-asset/punycode": "1.3.*",
                 "bower-asset/yii2-pjax": "~2.0.1",
-                "cebe/markdown": "~1.0.0 | ~1.1.0",
+                "cebe/markdown": "~1.0.0 | ~1.1.0 | ~1.2.0",
                 "ext-ctype": "*",
                 "ext-mbstring": "*",
                 "ezyang/htmlpurifier": "~4.6",
@@ -2084,7 +2084,7 @@
                 "framework",
                 "yii2"
             ],
-            "time": "2018-03-21T18:36:53+00:00"
+            "time": "2019-06-04T19:10:59+00:00"
         },
         {
             "name": "yiisoft/yii2-composer",
@@ -2142,16 +2142,16 @@
         },
         {
             "name": "yiisoft/yii2-queue",
-            "version": "2.2.0",
+            "version": "2.3.0",
             "source": {
                 "type": "git",
                 "url": "https://github.com/yiisoft/yii2-queue.git",
-                "reference": "d365e6f3222a0fdb150b1ea9f17bda2a4ddac61d"
+                "reference": "25c1142558768ec0e835171c972a4edc2fb59cf0"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/yiisoft/yii2-queue/zipball/d365e6f3222a0fdb150b1ea9f17bda2a4ddac61d",
-                "reference": "d365e6f3222a0fdb150b1ea9f17bda2a4ddac61d",
+                "url": "https://api.github.com/repos/yiisoft/yii2-queue/zipball/25c1142558768ec0e835171c972a4edc2fb59cf0",
+                "reference": "25c1142558768ec0e835171c972a4edc2fb59cf0",
                 "shasum": ""
             },
             "require": {
@@ -2161,7 +2161,8 @@
             },
             "require-dev": {
                 "aws/aws-sdk-php": ">=2.4",
-                "enqueue/amqp-lib": "^0.8",
+                "enqueue/amqp-lib": "^0.8||^0.9.10",
+                "enqueue/stomp": "^0.8.39",
                 "jeremeamia/superclosure": "*",
                 "pda/pheanstalk": "v3.*",
                 "php-amqplib/php-amqplib": "*",
@@ -2173,6 +2174,7 @@
             "suggest": {
                 "aws/aws-sdk-php": "Need for aws SQS.",
                 "enqueue/amqp-lib": "Need for AMQP interop queue.",
+                "enqueue/stomp": "Need for Stomp queue.",
                 "ext-gearman": "Need for Gearman queue.",
                 "ext-pcntl": "Need for process signals.",
                 "pda/pheanstalk": "Need for Beanstalk queue.",
@@ -2196,7 +2198,8 @@
                     "yii\\queue\\gearman\\": "src/drivers/gearman",
                     "yii\\queue\\redis\\": "src/drivers/redis",
                     "yii\\queue\\sync\\": "src/drivers/sync",
-                    "yii\\queue\\sqs\\": "src/drivers/sqs"
+                    "yii\\queue\\sqs\\": "src/drivers/sqs",
+                    "yii\\queue\\stomp\\": "src/drivers/stomp"
                 }
             },
             "notification-url": "https://packagist.org/downloads/",
@@ -2222,7 +2225,7 @@
                 "sqs",
                 "yii"
             ],
-            "time": "2019-03-19T22:36:41+00:00"
+            "time": "2019-06-04T18:58:40+00:00"
         },
         {
             "name": "yiisoft/yii2-redis",
@@ -6146,6 +6149,7 @@
     "prefer-lowest": false,
     "platform": {
         "php": "^7.2",
+        "ext-intl": "*",
         "ext-json": "*",
         "ext-libxml": "*",
         "ext-mbstring": "*",