I subscribe to both lists. From examining the mail headers,
here is a mail filtering algorithm that seems to deal with
duplicate posts showing up from the other group.
Create a cctalk and cctech saved mail folder
in this order:
put msgs with "To" header of either cctalk or classiccmp into cctalk
put msgs with "To" header of cctech into cctech
if "To" == cctalk and "Reply-To" == cctech, delete the message
if "To" == cctech and "Reply-To" == cctalk, delete the message
there are a couple stragglers for the case where "To" == classiccmp
but this got the bulk of the dups.