I've just waded through five long pages of  this thread from four years ago and had to chuckle at the very last line in the last post:
"it does get confusing when people uproot old threads that are now just simply out-dated."

The gist of the thread was that it's better to fail mail sent to your catchall/default account than to drop it into a blackhole. The reason given, as far as I understand, is that failing it keeps it out of the queues and frees up the LP server.

My question is does this apply when using the fail option in a filter list. Currently I have a couple of filters on the catchall account to pick out the mail that I want and a final rule that says "Discard Message" [blackhole] that "Has not previously been delivered". I wonder if changing it to fail will help the server in this case as the email is probably already in the queue. Can someone confirm or deny this.

I would like to change that Discard to Fail so that (a) authentic senders who make a typo might be notified and (b) spammers might eventually get the message that they're flogging a dead horse on this domain. If it makes it easier on the servers into the bargain then that's a bonus.

My concern is that innocent 3rd parties whose addresses have been spoofed will receive thousands of bounce messages. But I've been scanning the catchall spam for a while (about 3,000 per day) and I think most of the From addresses are made up rather than spoofed so there could be a bounced-bounce issue but at least individuals' inboxes wouldn't be impacted.

Any comments appreciated.