There is a new round of e-mails in circulation as far as I'm aware as I'm the second person to get an e-mail like this that I know of.
Upshot of it is, you will recieve an e-mail that would appear on the surface to be from a legitimate source (ie: your ISP or any mail server you may use).
In the Subject line there will be a message Failed Message, Failed Mail or Failed E-mail Message or some other variation on that.
There will be an Attachment with the e-mail(s) and for Goodness sakes don't open it!.
Just one in a long list of things that annoy me about the Internet these days.