I Didn't Get The Email-How Often It Happens

In the last 12 months, I have had three cases that I've labeled as "I didn't get the email" (IDGTE) cases.  It is often my role to help a judge or jury understand how email sent from one party  to another might not get delivered.  There are obvious reasons such as being removed by a SPAM filter.  However in most systems, you can see what file(s) the SPAM filter removed.  Thus, the recipient can figure out what happened.

But there are so-called silent lost email messages in which neither party is notified of the delivery failure and, in general, we never know what caused the failure.

 "Addressing Email Loss with SureMail: Measurement, Design, and Evaluation" measures such silent loss as approximately  0.71% to 1.02%.

This article caught my attention because most of the material that I have found on lost emails is aimed at bulk mailers, a far different situation than email between friends or business parties. I believe that the number IDGTE cases will continue to rise.  I'd like to hear from anyone who knows about  IDGTE cases.  I'm collecting a library of them.

Questions and comments are welcome.