You can easily setup PHPList for CritSend by editing a few configuration and administration files. 

In lists/config/config.php, the following lines should look like:
define ("TEST",0);
define("PHPMAILERHOST",'smtp.critsend.com');
$phpmailer_smtpuser = '';
$phpmailer_smtppassword = '';
$phpmailer_smtpsecure = 'tls';
$phpmailer_smtpport = '25';
In /lists/admin/class.phplistmailer.php, replace the if statement after "$this->Host = PHPMAILERHOST;" with this:
$this->Username = $GLOBALS['phpmailer_smtpuser'];
$this->Password = $GLOBALS['phpmailer_smtppassword'];
$this->SMTPSecure = $GLOBALS['phpmailer_smtpsecure'];
$this->Port = $GLOBALS['phpmailer_smtpport'];
Finally, In /lists/admin/phpmailer/class.smtp.php, replace:
$this->smtp_conn = fsockopen($host, # the host of the server
With:
$this->smtp_conn = fsockopen($host='tls://smtp.critsend.com',
That's it.