my guess as to why this continues to be a problem is that they see the paragraph of text in the response, and assume that it's a very wordy version of "it's fixed" without ever reading it. try being terse: "stop entering fake email addresses. just leave the field blank if they don't have one." next step after that is to actually call them on the phone.
@asuffield said:
Your users are clearly stupid. I recommend that you take this to management with a proposal for "extra training", and then every time you get one of these reports, the person who sent it is required to attend an extremely boring 1-hour seminar that explains how to use the application correctly.
Also, configure the system to reject no@email.com on the grounds that it is an invalid address (the email.com domain is squatted). That should shake them up a bit.
in general, this is a decent enough approach. making the training boring, however, won't solve anything; they're not likely to pay attention and actually learn anything then. better would be to get some dancing girls involved, or maybe a clown