Email scam ... what to do?

I have had several cases of contacts emailing me and they get the following response:

"mailer-daemon @talk talk.net re alixharkness@gmx.co.uk message undeliverable 550" This is not my email address at all. I do have a Talktalk busines account.

It has files attached ,,,which we have not opened. I found the person with that name and they had cancelled that email address a long time ago. What should I and my correspondents do about this?