why my emails go to junk mail :(

[eluser]Sumon[/eluser]
hi,
i use CI mail library to sending mail but it goes to spam for yahoo recipient. here is the code i use to send mail.

Code:

$this->load->library('email');

$config['protocol'] = 'sendmail';
$config['mailpath'] = '/usr/sbin/sendmail';
$config['charset'] = 'iso-8859-1';
$config['wordwrap'] = TRUE;

$this->email->initialize($config);

$this->email->from('[email protected]', 'My Company');
$this->email->to('[email protected]');
$this->email->subject('Email Test using CI');
$this->email->message('Testing the email class.');

$this->email->send();

echo $this->email->print_debugger();

please note that, i have created [email protected] from my cpanel. moreover, i register my domain at godaddy.com and my hosting company is internethostserver.com. in addition, gmail and hotmail users get message at inbox but yahoo user in spam folder.
any help or idea is highly appreciated.