RequestException in CurlFactory.php line 187:
cURL error 60: SSL certificate problem: unable to get local issuer certificate (see http://curl.haxx.se/libcurl/c/libcurl-errors.html)

MAIL_DRIVER=mailgun
MAIL_HOST=smtp.mailgun.org
MAIL_PORT=587
MAIL_USERNAME=myemail@gmail.com
MAIL_PASSWORD=mypassword
MAIL_ENCRYPTION=oEontENjBIdIrzaXhk9v9Q

public function mailContact(ContactRequest $request)
{
    $name = $request->input('name');
    $email = $request->input('email');
    $body = $request->input('body');
    $sent = Mail::send('emails.contact', compact('name', 'email', 'body'), function ($message) {
        $message->to('khudadadrs@gmail.com', 'Admin')->subject('Message');
    });

    if ($sent) {
        return Redirect::back()->withMessage('تشکر از اینکه تماس گرفتید.');
    }

    return Redirect::back()->withError('متاسفانه ایمیل ارسال نشد.دوباره تلاش کنید');
}

Edit For SSL EROR
vendor/guzzlehttp/guzzle/src/Handler/CurlFactory.php

search private function applyHandlerOptions(EasyHandle $easy, array &$conf)
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if ($options['verify'] === false) {
                unset($conf[CURLOPT_CAINFO]);
                $conf[CURLOPT_SSL_VERIFYHOST] = 0;
                $conf[CURLOPT_SSL_VERIFYPEER] = false;
            } else {
                $conf[CURLOPT_SSL_VERIFYHOST] = 2;
                $conf[CURLOPT_SSL_VERIFYPEER] = true;
----------------------------------------------------------
Change
----------------------------------------------------------
if ($options['verify'] === false) {
                unset($conf[CURLOPT_CAINFO]);
                $conf[CURLOPT_SSL_VERIFYHOST] = 0;
                $conf[CURLOPT_SSL_VERIFYPEER] = false;
            } else {
                $conf[CURLOPT_SSL_VERIFYHOST] = false;
                $conf[CURLOPT_SSL_VERIFYPEER] = false;
-----------------------------------------------------------