$message = array(
    'to'                => 'contato@dominio.com.br',
    'from_email'        => $_POST['email'],
    'from_name'         => $_POST['name'],
    'headers'           => array('reply-to: ' . $_POST['email'], 'from: ' . $_POST['email']),
    'subject'           => 'Contato do Site',
    'merge'             => 1,
    'global_merge_vars' => $data
);
$headers[] = 'From: '.$_POST["first_name"].' <'.$_POST["email"].'>';

wp_mail('contato@dominio.com.br', 'Qualquer texto', $conteudo, $headers);