<form method="POST">
    <h3>Editing: MailgunTransport.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php

namespace Illuminate\Mail\Transport;

use GuzzleHttp\ClientInterface;
use GuzzleHttp\Exception\GuzzleException;
use Swift_Mime_SimpleMessage;
use Swift_TransportException;

class MailgunTransport extends Transport
{
    /**
     * Guzzle client instance.
     *
     * @var \GuzzleHttp\ClientInterface
     */
    protected $client;

    /**
     * The Mailgun API key.
     *
     * @var string
     */
    protected $key;

    /**
     * The Mailgun email domain.
     *
     * @var string
     */
    protected $domain;

    /**
     * The Mailgun API endpoint.
     *
     * @var string
     */
    protected $endpoint;

    /**
     * Create a new Mailgun transport instance.
     *
     * @param  \GuzzleHttp\ClientInterface  $client
     * @param  string  $key
     * @param  string  $domain
     * @param  string|null  $endpoint
     * @return void
     */
    public function __construct(ClientInterface $client, $key, $domain, $endpoint = null)
    {
        $this-&gt;key = $key;
        $this-&gt;client = $client;
        $this-&gt;endpoint = $endpoint ?? 'api.mailgun.net';

        $this-&gt;setDomain($domain);
    }

    /**
     * {@inheritdoc}
     *
     * @return int
     */
    public function send(Swift_Mime_SimpleMessage $message, &amp;$failedRecipients = null)
    {
        $this-&gt;beforeSendPerformed($message);

        $to = $this-&gt;getTo($message);

        $bcc = $message-&gt;getBcc();

        $message-&gt;setBcc([]);

        try {
            $response = $this-&gt;client-&gt;request(
                'POST',
                &quot;https://{$this-&gt;endpoint}/v3/{$this-&gt;domain}/messages.mime&quot;,
                $this-&gt;payload($message, $to)
            );
        } catch (GuzzleException $e) {
            throw new Swift_TransportException('Request to Mailgun API failed.', $e-&gt;getCode(), $e);
        }

        $messageId = $this-&gt;getMessageId($response);

        $message-&gt;getHeaders()-&gt;addTextHeader('X-Message-ID', $messageId);
        $message-&gt;getHeaders()-&gt;addTextHeader('X-Mailgun-Message-ID', $messageId);

        $message-&gt;setBcc($bcc);

        $this-&gt;sendPerformed($message);

        return $this-&gt;numberOfRecipients($message);
    }

    /**
     * Get the HTTP payload for sending the Mailgun message.
     *
     * @param  \Swift_Mime_SimpleMessage  $message
     * @param  string  $to
     * @return array
     */
    protected function payload(Swift_Mime_SimpleMessage $message, $to)
    {
        return [
            'auth' =&gt; [
                'api',
                $this-&gt;key,
            ],
            'multipart' =&gt; [
                [
                    'name' =&gt; 'to',
                    'contents' =&gt; $to,
                ],
                [
                    'name' =&gt; 'message',
                    'contents' =&gt; $message-&gt;toString(),
                    'filename' =&gt; 'message.mime',
                ],
            ],
        ];
    }

    /**
     * Get the &quot;to&quot; payload field for the API request.
     *
     * @param  \Swift_Mime_SimpleMessage  $message
     * @return string
     */
    protected function getTo(Swift_Mime_SimpleMessage $message)
    {
        return collect($this-&gt;allContacts($message))-&gt;map(function ($display, $address) {
            return $display ? $display.&quot; &lt;{$address}&gt;&quot; : $address;
        })-&gt;values()-&gt;implode(',');
    }

    /**
     * Get all of the contacts for the message.
     *
     * @param  \Swift_Mime_SimpleMessage  $message
     * @return array
     */
    protected function allContacts(Swift_Mime_SimpleMessage $message)
    {
        return array_merge(
            (array) $message-&gt;getTo(), (array) $message-&gt;getCc(), (array) $message-&gt;getBcc()
        );
    }

    /**
     * Get the message ID from the response.
     *
     * @param  \Psr\Http\Message\ResponseInterface  $response
     * @return string
     */
    protected function getMessageId($response)
    {
        return object_get(
            json_decode($response-&gt;getBody()-&gt;getContents()), 'id'
        );
    }

    /**
     * Get the API key being used by the transport.
     *
     * @return string
     */
    public function getKey()
    {
        return $this-&gt;key;
    }

    /**
     * Set the API key being used by the transport.
     *
     * @param  string  $key
     * @return string
     */
    public function setKey($key)
    {
        return $this-&gt;key = $key;
    }

    /**
     * Get the domain being used by the transport.
     *
     * @return string
     */
    public function getDomain()
    {
        return $this-&gt;domain;
    }

    /**
     * Set the domain being used by the transport.
     *
     * @param  string  $domain
     * @return string
     */
    public function setDomain($domain)
    {
        return $this-&gt;domain = $domain;
    }

    /**
     * Get the API endpoint being used by the transport.
     *
     * @return string
     */
    public function getEndpoint()
    {
        return $this-&gt;endpoint;
    }

    /**
     * Set the API endpoint being used by the transport.
     *
     * @param  string  $endpoint
     * @return string
     */
    public function setEndpoint($endpoint)
    {
        return $this-&gt;endpoint = $endpoint;
    }
}
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