SMTP settings work from localhost but on server it doesn't with PHPMailer - email

Question

This is the issue what i am facing
Localhost
Test mail with SMTP settings work
New user creation mail using the above smtp settings work
Server
Test mail with SMTP settings work
New user creation mail using the above smtp settings doesn't work
I echoed the mail smtp settings in both the cases and they are exactly same. The error i am getting is
SMTP -> ERROR: Failed to connect to server: php_network_getaddresses:
getaddrinfo failed: Name or service not known (0)SMTP Connect()
failed.
Any suggestions would be helpful.
I further debug it. The behavior turns out to be wierd
if (isset($_POST['User']))
{
if (UserUtil::validateAndSaveUserData($model, $_POST))
{
$mailer = new UiMailer();
$mailer->setFrom('fromAddress', 'fromName');
$mailer->setTo('toaddress');
$mailer->setSubject('Test subject');
$mailer->setBody('Test Body');
$mailer->Mailer = 'smtp';
$mailer->Username = 'username';
$mailer->Password = 'password';
$mailer->Host = 'host';
$mailer->Port = 25;
$mailer->SMTPAuth = true;
$status = $mailer->send() ? true : false;
if($status == true)
{
print "Sucess";
}
else
{
print $mailer->ErrorInfo . "</br>";
print "Failuere";
}
exit;
}
}
If i comment the call if (UserUtil::validateAndSaveUserData($model, $_POST)), it works fine. In the function i am validating and saving models using Yii framework. I further debug the function. I have the following relation in the system
User has one person
User has one address
So in the above call, if i comment the address part which $model->address->attributes or $model->address->validate or $model->address->save(), it works fine. The save functionality for address works fine. There are no issues related to it.