title: How to check if an email attachment has been opened
body: <p>I am working on a study that sends people a PDF document with information about their health. The team would like to know if the person has actually opened the PDF document (a sign that they didn't just ignore the e-mail). I know that it'd be possible to do it with a link to an external file, but the users are much less likely to click on a URL and download it then they are to just view an attachment, and we don't want to do anything that might prevent the users from reading the information (we've already had people say they never received the message, and with further investigation they discovered they had, they had just ignored it).</p>
  
  <p>Another option is to request a read report, but this is only useful if it doesn't annoy the user (ie it does it automatically when the email is opened instead of requesting them to send one). We're currently looking into this as well, but the ability to check if the attachment has been opened is a much better idea.</p>
  
  <p>The email is generated in MS SQL and sent using the database mail system, and we have adobe acrobat pro, so creating scripts in pdfs is possible (although I'm not sure whether those scripts will be allowed to run).</p>
  
  <p>Thanks</p>