How to Send E-Mail using PHP

<form method="post" action="">
Sender Email: <input type="text" name="sender_email" size="18" />
Receipent Email: <input type="text" name="receipent_email" size="18" />
Mail Subject: <input type="text" name="email_subject" size="18" />
Email Message: <textarea name="message" rows="50" cols="6"></textarea>
<input type="submit" name="submit" value="Send Email" />
</form>

if(count($_POST) > 0)
{
 $sender_email = $_POST["sender_email"];
 $receipent_email = $_POST["receipent_email"];
 $email_subject = $_POST["email_subject"];
 $message = $_POST["message"];
 $result = mail($receipent_email, $email_subject, $message,"From: $sender_email\n");
 if($result) {
    echo "Mail has been send successfully.";
 }
 else {
    echo "There was a problem in sending email.";
 }
}