Getting Error while sending a mail through SwiftMail

Swift_TransportException: Connection could not be established with host cp-in-14.webhostbox.net [Connection refused #111] in /home/virtugxx/public_html/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/StreamBuffer.php:268

Most of the time it working fine but sometimes it throw the above exeption. Anyone please tell me what’s the reason. My configuration are as follows

‘mailer’ => [
‘class’ => ‘yii\swiftmailer\Mailer’,
‘viewPath’ => ‘@common/mail’,
‘transport’ => [
‘class’ => ‘Swift_SmtpTransport’,
‘host’ => ‘cp-in-14.webhostbox.net’,
‘username’ => ‘*****’,
‘password’ => '
’,
‘port’ => ‘465’,
‘encryption’ => ‘ssl’,
],
],

Network connection or server issues.