> in a timely manner.  They would like to have an acknowledgment sent back to
> the owner when each member receives the post.
 
This is a sticky problem, as it has to be implemented by the
receiving system, whatever that happens to be. Also, what does
'received' mean in this context? Accepted for delivery by the
machine? Actually processed by the user's mail reader? Read and
understood by the end user (if you can make this one work, I'll
pay money for the secret...) There are also a lot of thorny
privacy issues involved that we probably don't want to discuss
here...8-(.
 
> not all posts are timely.  Is there something that can be put either in the
> header or on the timely postings by the listowner that will accomplish this
> without too much hassle?
 
If you know all the recipients are on Unix systems running a
Berkeley-derived version of sendmail and the list has FULLHDRs
set as the default, you can include a Return-Receipt-to: header
and sendmail will generate a receipt to the address in the the
Return-Receipt-to: header when sendmail accepts the message for
delivery on the machine. Be aware that many sites disable this
feature, and modern sendmails ignore this header by default (you
have to explicitly set a compile-time flag to get support for
it). Most non-Unix systems ignore it completely.
 
There's no standard facility for delivery reciepts -- the IETF is
working on one, but it's a long way from being widely deployed.