Who hasn’t? After the email has been sent and the attachment has been pointed out again and again in the text, it is missing. We therefore recommend that you always attach the attachment to the mail first and only then write it. During the writing (“see appendix” or “in appendix”) you should always check briefly whether this is really attached. If not – short write pause, attach attachment and only then continue writing. With this system, you are guaranteed never to forget an attachment again