用于简报的PHP邮件程序不起作用

Question

I have wrote a script for sending newsletter emails, but it doesn't work, and I dont' know why
here is the code:

    $subject = $_POST['subject'];
    $body = $_POST['body'];
    $headers = "From: [e-mail]
";
    $headers .= "Content-Type: text/html; charset=ISO-8859-1
";
    try {
        $stmt = $db->prepare("SELECT * FROM `newsletter`");
        $stmt->execute();
        foreach($stmt as $row) {
            if(mail($row['email'], $subject, $body, $headers)) {
                echo "The email to " . $row['email'] . " was <font color=\"green\">successfully sent</sent>.<br />";
            } else {
                echo "The email to " . $row['email'] . " <font color=\"red\">failed</font>.<br />";
            }
        }
    } catch (PDOException $e) {
        echo "<p><b>Sorry the connection to the database failed with: {$e->getMessage()}</b></p>";
    }

When I run the code, the email seems sent, but my mailbox is empty

Thanks in advance