PhpMAIL () functions

PhpMAIL () function question & lt ;? Phpinclude_once ('Conn. php '); $ activationKey & nbsp ;=& nbsp; & nbsp; mt_rand () & nbsp ;. & nbsp; mt_rand () & nbsp ;. & nbsp; mt_rand () & nbsp ;. & php MAIL () function problems

Include_once ('Conn. php ');
$ ActivationKey = mt_rand (). mt_rand ();
$ Username = mysql_real_escape_string ($ _ POST [username]);
$ Password = mysql_real_escape_string ($ _ POST [pwd]);
$ Email = mysql_real_escape_string ($ _ POST [email]);
$ SQL = "INSERT INTO users (username, password, email, activationkey, status) VALUES
('$ Username',' $ password', '$ email', '$ activationkey', 'verify ')";

Echo "An email has been sent to $ _ POST [email] with an activation key. Please check your mail to complete registration .";
// Send activation Email
$ To = $ _ POST [email];
Echo $;
$ Subject = "hajin.com Registration ";
$ Message = "Welcome to our website! \ R \ rYou, or someone using your email address, has completed registration at hajin.com. You can complete registration by clicking the following link: \ rhttp. // www.YOURWEBSITE.com/verify.php? $ ActivationKey \ r \ rIf this is an error, ignore this email and you will be removed from our mailing list. \ r \ rRegards, \ hajin.com Team ";
$ Headers = 'from: bigboylike @ sina.com '. "\ r \ n ".
'Reply-To: bigboylike@sina.com '. "\ r \ n ".
'X-Mailer: PHP/'. phpversion ();
Mail ($ to, $ subject, $ message, $ headers );
?>

Error message: Warning: mail () [function. mail]: SMTP server response: 503 5.5.2 Need Rcpt command. in E: \ WEB \ goo \ yx. php on line 20 php email
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You must log on automatically. PHPMAILER is certainly one of the alternatives.
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It cannot be implemented to implement the function. you need to know more about it, or you can only stay at what level.