Add TLS v1.3 to SMTP connection - closes #5070

Author: freescout-help-desk

overrides/swiftmailer/swiftmailer/lib/classes/Swift/Transport/StreamBuffer.php

@@ -91,7 +91,12 @@ public function startTLS()
         // To support modern tls we allow explicit tls1.0, tls1.1, tls1.2
         // Ssl3 and older are not allowed because they are vulnerable
         // @TODO make tls arguments configurable
-        return stream_socket_enable_crypto($this->stream, true, STREAM_CRYPTO_METHOD_TLSv1_0_CLIENT | STREAM_CRYPTO_METHOD_TLSv1_1_CLIENT | STREAM_CRYPTO_METHOD_TLSv1_2_CLIENT);
+        $crypto_method  = STREAM_CRYPTO_METHOD_TLSv1_0_CLIENT | STREAM_CRYPTO_METHOD_TLSv1_1_CLIENT | STREAM_CRYPTO_METHOD_TLSv1_2_CLIENT;
+        // https://github.com/freescout-help-desk/freescout/issues/5070
+        if (defined('STREAM_CRYPTO_METHOD_TLSv1_3_CLIENT')) {
+            $crypto_method = $crypto_method | STREAM_CRYPTO_METHOD_TLSv1_3_CLIENT;
+        }
+        return stream_socket_enable_crypto($this->stream, true, $crypto_method);
     }
 
     /**