We had this problem a couple of times before, but speaking from the Usenet
Gateway side of things for HP3000-L:

Please - do not place delivery or read acknowledgements on posts to
HP3000-L.  Although many mailers discard read acknowledgements, some don't,
and send the things back to the list.

These, of course, then cross over to Usenet through the gateway.

Although the current problem is relatively low in volume - the last one was
not.

Your cooperation is appreciated greatly.

Regards,
Joe Geiser