Script stopped sending emails / Please help

[smartcard]

Following is the function in my PHP script to send the emails.  My current PHP version is 4.4.6 when ever I tried to send a email I am getting the "Error: it was not possible to send e-mail message"

 

Please help....

 

Function SendMail($to,$subject,&$body,&$headers)
{
  $return_path="";
  if(IsSet($this->delivery["Headers"]))
  {
   $headers_values=$this->delivery["Headers"];
   for($header=0,Reset($headers_values);$header<count($headers_values);$header++,Next($headers_values))
   {
    if(strtolower(Key($headers_values))=="return-path")
    {
     $return_path=$headers_values[Key($headers_values)];
     break;
    }
   }
   if(strlen($return_path))
   {
    if(!defined("PHP_OS"))
     return($this->OutputError("it is not possible to set the Return-Path header with your PHP version"));
    if(!strcmp(substr(PHP_OS,0,3),"WIN"))
     return($this->OutputError("it is not possible to set the Return-Path header directly from a PHP script on Windows"));
    if($this->GetPHPVersion()<4000005)
     return($this->OutputError("it is not possible to set the Return-Path header in PHP version older than 4.0.5"));
   }
  }
  $success=(strlen($return_path) ? mail($to,$subject,$body,$headers,"-f".$return_path) : mail($to,$subject,$body,$headers));
  return($success ? "" : $this->OutputError("it was not possible to send e-mail message"));
}