Something

#tested and working
location="/maildir/user/.mailing-lists.workaround-chitchat/cur"
location=${location%/*}
location=${location##*/}
echo "$location"

#need to convert the above, so it can be used in find -exec
echo "/maildir/user/.mailing-lists.workaround-chitchat/cur" | grep --regexp '????'

find "$maildir' -type d -name cur -exec grep --regexp '????' '{}' \;