diff --git a/extensions/swiftmailer/Mailer.php b/extensions/swiftmailer/Mailer.php
index 58f0f23..c00fad6 100644
--- a/extensions/swiftmailer/Mailer.php
+++ b/extensions/swiftmailer/Mailer.php
@@ -145,7 +145,7 @@ class Mailer extends BaseMailer
 					$transport->$name = $value;
 				} else {
 					$setter = 'set' . $name;
-					if (method_exists($transport, $setter)) {
+					if (method_exists($transport, $setter) || method_exists($transport, '__call')) {
 						$transport->$setter($value);
 					} else {
 						throw new InvalidConfigException('Setting unknown property: ' . get_class($transport) . '::' . $name);
diff --git a/tests/unit/extensions/swiftmailer/MailerTest.php b/tests/unit/extensions/swiftmailer/MailerTest.php
index 306e128..24602b2 100644
--- a/tests/unit/extensions/swiftmailer/MailerTest.php
+++ b/tests/unit/extensions/swiftmailer/MailerTest.php
@@ -53,6 +53,8 @@ class MailerTest extends VendorTestCase
 		$transportConfig = [
 			'class' => 'Swift_SmtpTransport',
 			'host' => 'localhost',
+			'username' => 'username',
+			'password' => 'password',
 		];
 		$mailer->setTransport($transportConfig);
 		$transport = $mailer->getTransport();