On Wed, 18 Apr 2007, Eric Thomas wrote:

>> As one really can't "unsend" what has been sent, especially once
>> delivered, any more than one can "unsay" what one has said and been
>> heard by others, what is this supposed to do?
>
> Seriously, I would love to see examples of what these messages look 
> like, so that I can have LISTSERV filter them automatically.

As I recall (no pun intended--OK, pun intended), the wording is 
"[Careless sender] would like to recall the message: [subject line]."