How does it work? When you send an email, Onlooker checks your message and looks for specific search terms in the text like "ATTACHED" and checks the number of attachments added to this email. There are a number of built in search terms for the most common phrases that people use when they mean to attach a file and users can even add their own search term if they find that they commonly use different phrases to indicate that a file should be attached. If Onlooker determines that you have forgotten to add your attachment it will prompt you with a message reminding you. Of course it is possible to quickly dismiss the message with a single click, or stop and add your attachment.