"LISTSERV site administrators' forum" <[log in to unmask]> 
wrote on 01/20/2005 09:09:20 AM:

> Good morning, all. I have an owner who received this message
> many times and claims to have only sent the message once. Any
> ideas why? Thanks.
> 
> 
> Your message  is being returned to  you unprocessed because it
>  appears to have
> already been distributed to the  ANTHROPOLOGY-MAJORS-L list.
> That is, a message
> with identical text (but possibly with  different mail
> headers) has been posted
> to the  list recently, either  by you or  by someone else.  If
> you have  a good
> reason to resend this  message to the list (for instance 
> because you have been
> notified of a hardware failure with loss of data), please
> alter the text of the
> message  in  some way  and  resend  it to  the  list.  Note
> that  altering  the
> "Subject:" line or  adding blank lines at  the top or bottom
> of  the message is
> not sufficient; you should instead add a  sentence or two at
> the top explaining
> why you are resending the message, so that the other
> subscribers understand why
> they are getting two copies of the same message. 


Is it possible that some server in the chain from him to the listserv host 
is sending duplicates?  The most common cause of that is a system that 
times out after sending the data, but before it sends a 250 Message 
Accepted.  The sending system isn't *sure* that the receiver got the 
message, so it tries again.