diff --git a/src/Symfony/Component/Mailer/Bridge/Amazon/Transport/SesApiTransport.php b/src/Symfony/Component/Mailer/Bridge/Amazon/Transport/SesApiTransport.php
index 22ef23e84b..c9cd0ad8cc 100644
--- a/src/Symfony/Component/Mailer/Bridge/Amazon/Transport/SesApiTransport.php
+++ b/src/Symfony/Component/Mailer/Bridge/Amazon/Transport/SesApiTransport.php
@@ -65,7 +65,7 @@ class SesApiTransport extends AbstractApiTransport
 
         $result = new \SimpleXMLElement($response->getContent(false));
         if (200 !== $response->getStatusCode()) {
-            throw new HttpTransportException(sprintf('Unable to send an email: %s (code %s).', $result->Error->Message, $result->Error->Code), $response);
+            throw new HttpTransportException(sprintf('Unable to send an email: %s (code %d).', $result->Error->Message, $result->Error->Code), $response);
         }
 
         $property = $payload['Action'].'Result';
diff --git a/src/Symfony/Component/Mailer/Bridge/Amazon/Transport/SesHttpTransport.php b/src/Symfony/Component/Mailer/Bridge/Amazon/Transport/SesHttpTransport.php
index 1bb6c5486e..9cedbdf4c7 100644
--- a/src/Symfony/Component/Mailer/Bridge/Amazon/Transport/SesHttpTransport.php
+++ b/src/Symfony/Component/Mailer/Bridge/Amazon/Transport/SesHttpTransport.php
@@ -65,7 +65,7 @@ class SesHttpTransport extends AbstractHttpTransport
 
         $result = new \SimpleXMLElement($response->getContent(false));
         if (200 !== $response->getStatusCode()) {
-            throw new HttpTransportException(sprintf('Unable to send an email: %s (code %s).', $result->Error->Message, $result->Error->Code), $response);
+            throw new HttpTransportException(sprintf('Unable to send an email: %s (code %d).', $result->Error->Message, $result->Error->Code), $response);
         }
 
         $message->setMessageId($result->SendRawEmailResult->MessageId);
diff --git a/src/Symfony/Component/Mailer/Bridge/Mailchimp/Transport/MandrillApiTransport.php b/src/Symfony/Component/Mailer/Bridge/Mailchimp/Transport/MandrillApiTransport.php
index af221ca66e..9b7c181b29 100644
--- a/src/Symfony/Component/Mailer/Bridge/Mailchimp/Transport/MandrillApiTransport.php
+++ b/src/Symfony/Component/Mailer/Bridge/Mailchimp/Transport/MandrillApiTransport.php
@@ -51,10 +51,10 @@ class MandrillApiTransport extends AbstractApiTransport
         $result = $response->toArray(false);
         if (200 !== $response->getStatusCode()) {
             if ('error' === ($result['status'] ?? false)) {
-                throw new HttpTransportException(sprintf('Unable to send an email: %s (code %s).', $result['message'], $result['code']), $response);
+                throw new HttpTransportException(sprintf('Unable to send an email: %s (code %d).', $result['message'], $result['code']), $response);
             }
 
-            throw new HttpTransportException(sprintf('Unable to send an email (code %s).', $result['code']), $response);
+            throw new HttpTransportException(sprintf('Unable to send an email (code %d).', $result['code']), $response);
         }
 
         $firstRecipient = reset($result);
diff --git a/src/Symfony/Component/Mailer/Bridge/Mailchimp/Transport/MandrillHttpTransport.php b/src/Symfony/Component/Mailer/Bridge/Mailchimp/Transport/MandrillHttpTransport.php
index 6ead154906..92f90b8563 100644
--- a/src/Symfony/Component/Mailer/Bridge/Mailchimp/Transport/MandrillHttpTransport.php
+++ b/src/Symfony/Component/Mailer/Bridge/Mailchimp/Transport/MandrillHttpTransport.php
@@ -58,10 +58,10 @@ class MandrillHttpTransport extends AbstractHttpTransport
         $result = $response->toArray(false);
         if (200 !== $response->getStatusCode()) {
             if ('error' === ($result['status'] ?? false)) {
-                throw new HttpTransportException(sprintf('Unable to send an email: %s (code %s).', $result['message'], $result['code']), $response);
+                throw new HttpTransportException(sprintf('Unable to send an email: %s (code %d).', $result['message'], $result['code']), $response);
             }
 
-            throw new HttpTransportException(sprintf('Unable to send an email (code %s).', $result['code']), $response);
+            throw new HttpTransportException(sprintf('Unable to send an email (code %d).', $result['code']), $response);
         }
 
         $message->setMessageId($result[0]['_id']);
diff --git a/src/Symfony/Component/Mailer/Bridge/Mailgun/Transport/MailgunApiTransport.php b/src/Symfony/Component/Mailer/Bridge/Mailgun/Transport/MailgunApiTransport.php
index cf40a8cf1e..c8ed383fcc 100644
--- a/src/Symfony/Component/Mailer/Bridge/Mailgun/Transport/MailgunApiTransport.php
+++ b/src/Symfony/Component/Mailer/Bridge/Mailgun/Transport/MailgunApiTransport.php
@@ -65,10 +65,10 @@ class MailgunApiTransport extends AbstractApiTransport
         $result = $response->toArray(false);
         if (200 !== $response->getStatusCode()) {
             if ('application/json' === $response->getHeaders(false)['content-type'][0]) {
-                throw new HttpTransportException(sprintf('Unable to send an email: %s (code %s).', $result['message'], $response->getStatusCode()), $response);
+                throw new HttpTransportException(sprintf('Unable to send an email: %s (code %d).', $result['message'], $response->getStatusCode()), $response);
             }
 
-            throw new HttpTransportException(sprintf('Unable to send an email: %s (code %s).', $response->getContent(false), $response->getStatusCode()), $response);
+            throw new HttpTransportException(sprintf('Unable to send an email: %s (code %d).', $response->getContent(false), $response->getStatusCode()), $response);
         }
 
         $sentMessage->setMessageId($result['id']);
diff --git a/src/Symfony/Component/Mailer/Bridge/Mailgun/Transport/MailgunHttpTransport.php b/src/Symfony/Component/Mailer/Bridge/Mailgun/Transport/MailgunHttpTransport.php
index a42598a0b5..3ed6f73369 100644
--- a/src/Symfony/Component/Mailer/Bridge/Mailgun/Transport/MailgunHttpTransport.php
+++ b/src/Symfony/Component/Mailer/Bridge/Mailgun/Transport/MailgunHttpTransport.php
@@ -67,10 +67,10 @@ class MailgunHttpTransport extends AbstractHttpTransport
         $result = $response->toArray(false);
         if (200 !== $response->getStatusCode()) {
             if ('application/json' === $response->getHeaders(false)['content-type'][0]) {
-                throw new HttpTransportException(sprintf('Unable to send an email: %s (code %s).', $result['message'], $response->getStatusCode()), $response);
+                throw new HttpTransportException(sprintf('Unable to send an email: %s (code %d).', $result['message'], $response->getStatusCode()), $response);
             }
 
-            throw new HttpTransportException(sprintf('Unable to send an email: %s (code %s).', $response->getContent(false), $response->getStatusCode()), $response);
+            throw new HttpTransportException(sprintf('Unable to send an email: %s (code %d).', $response->getContent(false), $response->getStatusCode()), $response);
         }
 
         $message->setMessageId($result['id']);
diff --git a/src/Symfony/Component/Mailer/Bridge/Postmark/Transport/PostmarkApiTransport.php b/src/Symfony/Component/Mailer/Bridge/Postmark/Transport/PostmarkApiTransport.php
index 610f858260..352b2eded1 100644
--- a/src/Symfony/Component/Mailer/Bridge/Postmark/Transport/PostmarkApiTransport.php
+++ b/src/Symfony/Component/Mailer/Bridge/Postmark/Transport/PostmarkApiTransport.php
@@ -54,7 +54,7 @@ class PostmarkApiTransport extends AbstractApiTransport
 
         $result = $response->toArray(false);
         if (200 !== $response->getStatusCode()) {
-            throw new HttpTransportException(sprintf('Unable to send an email: %s (code %s).', $result['Message'], $result['ErrorCode']), $response);
+            throw new HttpTransportException(sprintf('Unable to send an email: %s (code %d).', $result['Message'], $result['ErrorCode']), $response);
         }
 
         $sentMessage->setMessageId($result['MessageID']);
diff --git a/src/Symfony/Component/Mailer/Bridge/Sendgrid/Transport/SendgridApiTransport.php b/src/Symfony/Component/Mailer/Bridge/Sendgrid/Transport/SendgridApiTransport.php
index df90d21472..550fd4bf33 100644
--- a/src/Symfony/Component/Mailer/Bridge/Sendgrid/Transport/SendgridApiTransport.php
+++ b/src/Symfony/Component/Mailer/Bridge/Sendgrid/Transport/SendgridApiTransport.php
@@ -53,7 +53,7 @@ class SendgridApiTransport extends AbstractApiTransport
         if (202 !== $response->getStatusCode()) {
             $errors = $response->toArray(false);
 
-            throw new HttpTransportException(sprintf('Unable to send an email: %s (code %s).', implode('; ', array_column($errors['errors'], 'message')), $response->getStatusCode()), $response);
+            throw new HttpTransportException(sprintf('Unable to send an email: %s (code %d).', implode('; ', array_column($errors['errors'], 'message')), $response->getStatusCode()), $response);
         }
 
         $sentMessage->setMessageId($response->getHeaders(false)['x-message-id'][0]);