def get_docomo_post_data(number, hidden_param):
    """Returns a mapping for POST data to Docomo's url to inquire for messages
    for the given number.
    Args:
        number: a normalized mobile number.
    Returns:
        a mapping for the POST data.
    """
    return {'es': 1,
            'si': 1,
            'bi1': 1,
            'ep': hidden_param,
            'sm': number}