Zend_Mail sent email is treated as SPAM

[martincho]

Please tell me what I am doing wrong. I am sending an email using the Zend_Mail class like this:\[code\]$message = <<<STRYou have a new invoice!Sign in to your clientarea to see it.Best regards,Company nameSTR;$mail = new Zend_Mail();$mail->setBodyText($message);$mail->setFrom('[email protected]', 'Company.com');$mail->addTo('[email protected]', 'Client Name');$mail->setSubject('You have a new invoice!');$mail->send();\[/code\]It is received as a spam though. There are other applications such as Webmin on my server and emails they send is not treated as SPAM.