Yeah, your code needs to add 'additional-headers'. but before, you must know that the second argument of mail() function is a subject. You can't a HTML code in subject.
Your program would send a message in plain-text mode not in HTML.
Add this additional header and try again.
<?
$to='mandar@freeos.com';
$subject = "Hi 🙂";
$body='<body>Hi i am mandar</body>';
$add_header = "Content-Type: text/html; charset=iso-8859-1\n"; // your mail client will recognize that this mail is HTML type.
$add_header .= "From: FLUTIA <neowinny@nownuri.net>\n";
mail( $to, $subject, $body, $add_header );
?>
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