def _parse_outgoing_mail(sender, to, msgstring):
    """
    Parse an outgoing mail and put it into the OUTBOX.


    Arguments:
    - `sender`: str
    - `to`: str
    - `msgstring`: str

    Return: None
    Exceptions: None
    """
    global OUTBOX
    OUTBOX.append(email.message_from_string(msgstring))
    return