diff --git a/src/Symfony/Component/Mailer/Bridge/Amazon/Transport/SesSmtpTransport.php b/src/Symfony/Component/Mailer/Bridge/Amazon/Transport/SesSmtpTransport.php
index 08146ab0d9..2c53200689 100644
--- a/src/Symfony/Component/Mailer/Bridge/Amazon/Transport/SesSmtpTransport.php
+++ b/src/Symfony/Component/Mailer/Bridge/Amazon/Transport/SesSmtpTransport.php
@@ -25,7 +25,7 @@ class SesSmtpTransport extends EsmtpTransport
      */
     public function __construct(string $username, string $password, string $region = null, EventDispatcherInterface $dispatcher = null, LoggerInterface $logger = null)
     {
-        parent::__construct(sprintf('email-smtp.%s.amazonaws.com', $region ?: 'eu-west-1'), 587, true, null, $dispatcher, $logger);
+        parent::__construct(sprintf('email-smtp.%s.amazonaws.com', $region ?: 'eu-west-1'), 587, true, $dispatcher, $logger);
 
         $this->setUsername($username);
         $this->setPassword($password);
diff --git a/src/Symfony/Component/Mailer/Bridge/Google/Transport/GmailSmtpTransport.php b/src/Symfony/Component/Mailer/Bridge/Google/Transport/GmailSmtpTransport.php
index 371877e535..19402fccf5 100644
--- a/src/Symfony/Component/Mailer/Bridge/Google/Transport/GmailSmtpTransport.php
+++ b/src/Symfony/Component/Mailer/Bridge/Google/Transport/GmailSmtpTransport.php
@@ -22,7 +22,7 @@ class GmailSmtpTransport extends EsmtpTransport
 {
     public function __construct(string $username, string $password, EventDispatcherInterface $dispatcher = null, LoggerInterface $logger = null)
     {
-        parent::__construct('smtp.gmail.com', 465, true, null, $dispatcher, $logger);
+        parent::__construct('smtp.gmail.com', 465, true, $dispatcher, $logger);
 
         $this->setUsername($username);
         $this->setPassword($password);
diff --git a/src/Symfony/Component/Mailer/Bridge/Mailchimp/Transport/MandrillSmtpTransport.php b/src/Symfony/Component/Mailer/Bridge/Mailchimp/Transport/MandrillSmtpTransport.php
index bdcb4f055c..72d2e8a51a 100644
--- a/src/Symfony/Component/Mailer/Bridge/Mailchimp/Transport/MandrillSmtpTransport.php
+++ b/src/Symfony/Component/Mailer/Bridge/Mailchimp/Transport/MandrillSmtpTransport.php
@@ -22,7 +22,7 @@ class MandrillSmtpTransport extends EsmtpTransport
 {
     public function __construct(string $username, string $password, EventDispatcherInterface $dispatcher = null, LoggerInterface $logger = null)
     {
-        parent::__construct('smtp.mandrillapp.com', 587, true, null, $dispatcher, $logger);
+        parent::__construct('smtp.mandrillapp.com', 587, true, $dispatcher, $logger);
 
         $this->setUsername($username);
         $this->setPassword($password);
diff --git a/src/Symfony/Component/Mailer/Bridge/Mailgun/Transport/MailgunSmtpTransport.php b/src/Symfony/Component/Mailer/Bridge/Mailgun/Transport/MailgunSmtpTransport.php
index b2e15b594b..824cd48b03 100644
--- a/src/Symfony/Component/Mailer/Bridge/Mailgun/Transport/MailgunSmtpTransport.php
+++ b/src/Symfony/Component/Mailer/Bridge/Mailgun/Transport/MailgunSmtpTransport.php
@@ -22,7 +22,7 @@ class MailgunSmtpTransport extends EsmtpTransport
 {
     public function __construct(string $username, string $password, string $region = null, EventDispatcherInterface $dispatcher = null, LoggerInterface $logger = null)
     {
-        parent::__construct('us' !== ($region ?: 'us') ? sprintf('smtp.%s.mailgun.org', $region) : 'smtp.mailgun.org', 465, true, null, $dispatcher, $logger);
+        parent::__construct('us' !== ($region ?: 'us') ? sprintf('smtp.%s.mailgun.org', $region) : 'smtp.mailgun.org', 465, true, $dispatcher, $logger);
 
         $this->setUsername($username);
         $this->setPassword($password);
diff --git a/src/Symfony/Component/Mailer/Bridge/Postmark/Transport/PostmarkSmtpTransport.php b/src/Symfony/Component/Mailer/Bridge/Postmark/Transport/PostmarkSmtpTransport.php
index f9f32ed7e4..395b638c56 100644
--- a/src/Symfony/Component/Mailer/Bridge/Postmark/Transport/PostmarkSmtpTransport.php
+++ b/src/Symfony/Component/Mailer/Bridge/Postmark/Transport/PostmarkSmtpTransport.php
@@ -22,7 +22,7 @@ class PostmarkSmtpTransport extends EsmtpTransport
 {
     public function __construct(string $id, EventDispatcherInterface $dispatcher = null, LoggerInterface $logger = null)
     {
-        parent::__construct('smtp.postmarkapp.com', 587, true, null, $dispatcher, $logger);
+        parent::__construct('smtp.postmarkapp.com', 587, true, $dispatcher, $logger);
 
         $this->setUsername($id);
         $this->setPassword($id);
diff --git a/src/Symfony/Component/Mailer/Bridge/Sendgrid/Transport/SendgridSmtpTransport.php b/src/Symfony/Component/Mailer/Bridge/Sendgrid/Transport/SendgridSmtpTransport.php
index d61eca3c1c..90d6dc60db 100644
--- a/src/Symfony/Component/Mailer/Bridge/Sendgrid/Transport/SendgridSmtpTransport.php
+++ b/src/Symfony/Component/Mailer/Bridge/Sendgrid/Transport/SendgridSmtpTransport.php
@@ -22,7 +22,7 @@ class SendgridSmtpTransport extends EsmtpTransport
 {
     public function __construct(string $key, EventDispatcherInterface $dispatcher = null, LoggerInterface $logger = null)
     {
-        parent::__construct('smtp.sendgrid.net', 465, true, null, $dispatcher, $logger);
+        parent::__construct('smtp.sendgrid.net', 465, true, $dispatcher, $logger);
 
         $this->setUsername('apikey');
         $this->setPassword($key);
diff --git a/src/Symfony/Component/Mailer/CHANGELOG.md b/src/Symfony/Component/Mailer/CHANGELOG.md
index fc642f576d..b033405850 100644
--- a/src/Symfony/Component/Mailer/CHANGELOG.md
+++ b/src/Symfony/Component/Mailer/CHANGELOG.md
@@ -4,6 +4,7 @@ CHANGELOG
 4.4.0
 -----
 
+ * [BC BREAK] removed the `auth_mode` DSN option (it is now always determined automatically)
  * STARTTLS cannot be enabled anymore (it is used automatically if TLS is disabled and the server supports STARTTLS)
  * [BC BREAK] Removed the `encryption` DSN option (use `smtps` instead)
  * Added support for the `smtps` protocol (does the same as using `smtp` and port `465`)
diff --git a/src/Symfony/Component/Mailer/Tests/Transport/Smtp/EsmtpTransportFactoryTest.php b/src/Symfony/Component/Mailer/Tests/Transport/Smtp/EsmtpTransportFactoryTest.php
index c64854239c..a3b13b624c 100644
--- a/src/Symfony/Component/Mailer/Tests/Transport/Smtp/EsmtpTransportFactoryTest.php
+++ b/src/Symfony/Component/Mailer/Tests/Transport/Smtp/EsmtpTransportFactoryTest.php
@@ -38,30 +38,30 @@ class EsmtpTransportFactoryTest extends TransportFactoryTestCase
         $eventDispatcher = $this->getDispatcher();
         $logger = $this->getLogger();
 
-        $transport = new EsmtpTransport('localhost', 25, false, null, $eventDispatcher, $logger);
+        $transport = new EsmtpTransport('localhost', 25, false, $eventDispatcher, $logger);
 
         yield [
             new Dsn('smtp', 'localhost'),
             $transport,
         ];
 
-        $transport = new EsmtpTransport('example.com', 99, true, 'login', $eventDispatcher, $logger);
+        $transport = new EsmtpTransport('example.com', 99, true, $eventDispatcher, $logger);
         $transport->setUsername(self::USER);
         $transport->setPassword(self::PASSWORD);
 
         yield [
-            new Dsn('smtps', 'example.com', self::USER, self::PASSWORD, 99, ['auth_mode' => 'login']),
+            new Dsn('smtps', 'example.com', self::USER, self::PASSWORD, 99),
             $transport,
         ];
 
-        $transport = new EsmtpTransport('example.com', 465, true, null, $eventDispatcher, $logger);
+        $transport = new EsmtpTransport('example.com', 465, true, $eventDispatcher, $logger);
 
         yield [
             new Dsn('smtps', 'example.com'),
             $transport,
         ];
 
-        $transport = new EsmtpTransport('example.com', 465, true, null, $eventDispatcher, $logger);
+        $transport = new EsmtpTransport('example.com', 465, true, $eventDispatcher, $logger);
 
         yield [
             new Dsn('smtp', 'example.com', '', '', 465),
diff --git a/src/Symfony/Component/Mailer/Transport/Smtp/EsmtpTransport.php b/src/Symfony/Component/Mailer/Transport/Smtp/EsmtpTransport.php
index ef4d7f71cc..85809e8f64 100644
--- a/src/Symfony/Component/Mailer/Transport/Smtp/EsmtpTransport.php
+++ b/src/Symfony/Component/Mailer/Transport/Smtp/EsmtpTransport.php
@@ -29,12 +29,12 @@ class EsmtpTransport extends SmtpTransport
     private $authenticators = [];
     private $username = '';
     private $password = '';
-    private $authMode;
 
-    public function __construct(string $host = 'localhost', int $port = 0, bool $tls = null, string $authMode = null, EventDispatcherInterface $dispatcher = null, LoggerInterface $logger = null)
+    public function __construct(string $host = 'localhost', int $port = 0, bool $tls = null, EventDispatcherInterface $dispatcher = null, LoggerInterface $logger = null)
     {
         parent::__construct(null, $dispatcher, $logger);
 
+        // order is important here (roughly most secure and popular first)
         $this->authenticators = [
             new Auth\CramMd5Authenticator(),
             new Auth\LoginAuthenticator(),
@@ -61,9 +61,6 @@ class EsmtpTransport extends SmtpTransport
 
         $stream->setHost($host);
         $stream->setPort($port);
-        if (null !== $authMode) {
-            $this->setAuthMode($authMode);
-        }
     }
 
     public function setUsername(string $username): self
@@ -90,18 +87,6 @@ class EsmtpTransport extends SmtpTransport
         return $this->password;
     }
 
-    public function setAuthMode(string $mode): self
-    {
-        $this->authMode = $mode;
-
-        return $this;
-    }
-
-    public function getAuthMode(): string
-    {
-        return $this->authMode;
-    }
-
     public function addAuthenticator(AuthenticatorInterface $authenticator): void
     {
         $this->authenticators[] = $authenticator;
@@ -166,7 +151,7 @@ class EsmtpTransport extends SmtpTransport
         $authNames = [];
         $errors = [];
         $modes = array_map('strtolower', $modes);
-        foreach ($this->getActiveAuthenticators() as $authenticator) {
+        foreach ($this->authenticators as $authenticator) {
             if (!\in_array(strtolower($authenticator->getAuthKeyword()), $modes, true)) {
                 continue;
             }
@@ -195,22 +180,4 @@ class EsmtpTransport extends SmtpTransport
 
         throw new TransportException($message);
     }
-
-    /**
-     * @return AuthenticatorInterface[]
-     */
-    private function getActiveAuthenticators(): array
-    {
-        if (!$mode = strtolower($this->authMode)) {
-            return $this->authenticators;
-        }
-
-        foreach ($this->authenticators as $authenticator) {
-            if (strtolower($authenticator->getAuthKeyword()) === $mode) {
-                return [$authenticator];
-            }
-        }
-
-        throw new TransportException(sprintf('Auth mode "%s" is invalid.', $mode));
-    }
 }
diff --git a/src/Symfony/Component/Mailer/Transport/Smtp/EsmtpTransportFactory.php b/src/Symfony/Component/Mailer/Transport/Smtp/EsmtpTransportFactory.php
index 377a36e3ef..a1438f91f4 100644
--- a/src/Symfony/Component/Mailer/Transport/Smtp/EsmtpTransportFactory.php
+++ b/src/Symfony/Component/Mailer/Transport/Smtp/EsmtpTransportFactory.php
@@ -23,11 +23,10 @@ final class EsmtpTransportFactory extends AbstractTransportFactory
     public function create(Dsn $dsn): TransportInterface
     {
         $tls = 'smtps' === $dsn->getScheme() ? true : null;
-        $authMode = $dsn->getOption('auth_mode');
         $port = $dsn->getPort(0);
         $host = $dsn->getHost();
 
-        $transport = new EsmtpTransport($host, $port, $tls, $authMode, $this->dispatcher, $this->logger);
+        $transport = new EsmtpTransport($host, $port, $tls, $this->dispatcher, $this->logger);
 
         if ($user = $dsn->getUser()) {
             $transport->setUsername($user);