[Mailer] fixed error that is masked by another error

Author: fabpot

Transport/Smtp/SmtpTransport.php

@@ -114,7 +114,11 @@ public function send(RawMessage $message, SmtpEnvelope $envelope = null): ?SentM
         try {
             $message = parent::send($message, $envelope);
         } catch (TransportExceptionInterface $e) {
-            $this->executeCommand("RSET\r\n", [250]);
+            try {
+                $this->executeCommand("RSET\r\n", [250]);
+            } catch (TransportExceptionInterface $_) {
+                // ignore this exception as it probably means that the server error was final
+            }
 
             throw $e;
         }