diff --git a/src/Mailgun/Messages/MessageBuilder.php b/src/Mailgun/Messages/MessageBuilder.php
index f63f183..ca7714c 100644
--- a/src/Mailgun/Messages/MessageBuilder.php
+++ b/src/Mailgun/Messages/MessageBuilder.php
@@ -102,7 +102,7 @@ class MessageBuilder
         }
         $fullName = $this->getFullName($variables);
         if ($fullName != null) {
-            return "'$fullName' <$address>";
+            return sprintf('"%s" <%s>', $fullName, $address);
         }
 
         return $address;
diff --git a/tests/Messages/BatchMessageTest.php b/tests/Messages/BatchMessageTest.php
index d086b1e..7edf6b2 100644
--- a/tests/Messages/BatchMessageTest.php
+++ b/tests/Messages/BatchMessageTest.php
@@ -32,7 +32,7 @@ class BatchMessageTest extends \Mailgun\Tests\MailgunTestCase
         $message = $this->client->BatchMessage($this->sampleDomain);
         $message->addToRecipient('test@samples.mailgun.org', ['first' => 'Test', 'last' => 'User']);
         $messageObj = $message->getMessage();
-        $this->assertEquals(['to' => ["'Test User' <test@samples.mailgun.org>"]], $messageObj);
+        $this->assertEquals(['to' => ['"Test User" <test@samples.mailgun.org>']], $messageObj);
 
         $reflectionClass = new \ReflectionClass(get_class($message));
         $property = $reflectionClass->getProperty('counters');
@@ -60,7 +60,7 @@ class BatchMessageTest extends \Mailgun\Tests\MailgunTestCase
         $message = $this->client->BatchMessage($this->sampleDomain);
         $message->addToRecipient('test@samples.mailgun.org', ['first' => 'Test', 'last' => 'User']);
         $messageObj = $message->getMessage();
-        $this->assertEquals(['to' => ["'Test User' <test@samples.mailgun.org>"]], $messageObj);
+        $this->assertEquals(['to' => ['"Test User" <test@samples.mailgun.org>']], $messageObj);
 
         $reflectionClass = new \ReflectionClass(get_class($message));
         $property = $reflectionClass->getProperty('batchRecipientAttributes');
@@ -75,7 +75,7 @@ class BatchMessageTest extends \Mailgun\Tests\MailgunTestCase
         $message = $this->client->BatchMessage($this->sampleDomain);
         $message->addCcRecipient('test@samples.mailgun.org', ['first' => 'Test', 'last' => 'User']);
         $messageObj = $message->getMessage();
-        $this->assertEquals(['cc' => ["'Test User' <test@samples.mailgun.org>"]], $messageObj);
+        $this->assertEquals(['cc' => ['"Test User" <test@samples.mailgun.org>']], $messageObj);
 
         $reflectionClass = new \ReflectionClass(get_class($message));
         $property = $reflectionClass->getProperty('batchRecipientAttributes');
@@ -90,7 +90,7 @@ class BatchMessageTest extends \Mailgun\Tests\MailgunTestCase
         $message = $this->client->BatchMessage($this->sampleDomain);
         $message->addBccRecipient('test@samples.mailgun.org', ['first' => 'Test', 'last' => 'User']);
         $messageObj = $message->getMessage();
-        $this->assertEquals(['bcc' => ["'Test User' <test@samples.mailgun.org>"]], $messageObj);
+        $this->assertEquals(['bcc' => ['"Test User" <test@samples.mailgun.org>']], $messageObj);
 
         $reflectionClass = new \ReflectionClass(get_class($message));
         $property = $reflectionClass->getProperty('batchRecipientAttributes');
diff --git a/tests/Messages/MessageBuilderTest.php b/tests/Messages/MessageBuilderTest.php
index 6efadde..cd058ed 100644
--- a/tests/Messages/MessageBuilderTest.php
+++ b/tests/Messages/MessageBuilderTest.php
@@ -48,7 +48,7 @@ class MessageBuilderTest extends \Mailgun\Tests\MailgunTestCase
         $message = $this->client->MessageBuilder();
         $message->addToRecipient('test@samples.mailgun.org', ['first' => 'Test', 'last' => 'User']);
         $messageObj = $message->getMessage();
-        $this->assertEquals(['to' => ["'Test User' <test@samples.mailgun.org>"]], $messageObj);
+        $this->assertEquals(['to' => ['"Test User" <test@samples.mailgun.org>']], $messageObj);
     }
 
     public function testAddCcRecipient()
@@ -56,7 +56,7 @@ class MessageBuilderTest extends \Mailgun\Tests\MailgunTestCase
         $message = $this->client->MessageBuilder();
         $message->addCcRecipient('test@samples.mailgun.org', ['first' => 'Test', 'last' => 'User']);
         $messageObj = $message->getMessage();
-        $this->assertEquals(['cc' => ["'Test User' <test@samples.mailgun.org>"]], $messageObj);
+        $this->assertEquals(['cc' => ['"Test User" <test@samples.mailgun.org>']], $messageObj);
     }
 
     public function testAddBccRecipient()
@@ -64,7 +64,7 @@ class MessageBuilderTest extends \Mailgun\Tests\MailgunTestCase
         $message = $this->client->MessageBuilder();
         $message->addBccRecipient('test@samples.mailgun.org', ['first' => 'Test', 'last' => 'User']);
         $messageObj = $message->getMessage();
-        $this->assertEquals(['bcc' => ["'Test User' <test@samples.mailgun.org>"]], $messageObj);
+        $this->assertEquals(['bcc' => ['"Test User" <test@samples.mailgun.org>']], $messageObj);
     }
 
     public function testToRecipientCount()
@@ -108,7 +108,7 @@ class MessageBuilderTest extends \Mailgun\Tests\MailgunTestCase
         $message = $this->client->MessageBuilder();
         $message->setFromAddress('test@samples.mailgun.org', ['first' => 'Test', 'last' => 'User']);
         $messageObj = $message->getMessage();
-        $this->assertEquals(['from' => ["'Test User' <test@samples.mailgun.org>"]], $messageObj);
+        $this->assertEquals(['from' => ['"Test User" <test@samples.mailgun.org>']], $messageObj);
     }
 
     public function testSetReplyTo()
@@ -117,7 +117,7 @@ class MessageBuilderTest extends \Mailgun\Tests\MailgunTestCase
         $message->setReplyToAddress('overwritten@samples.mailgun.org');
         $message->setReplyToAddress('test@samples.mailgun.org', ['first' => 'Test', 'last' => 'User']);
         $messageObj = $message->getMessage();
-        $this->assertEquals(['h:reply-to' => "'Test User' <test@samples.mailgun.org>"], $messageObj);
+        $this->assertEquals(['h:reply-to' => '"Test User" <test@samples.mailgun.org>'], $messageObj);
     }
 
     public function testSetSubject()