Yes, I finally was able to get that to work - however my tests show that it will only produce the custom 404 page with existing links in an email. If a user somehow requests any other type of URL that is still directed at the phplist install, they get a standard 404 message.
More importantly however, is the real reason for my question which I never made entirely clear and maybe should be another thread - let me know if I should make the following elaboration on this question, a different thread:
If someone is blacklisted, they are still able to click links and get properly re-directed. However, I’m wondering if it’s possible that once someone is blacklisted can we have an option to send them to a custom URL?
The reason is if someone is blacklisted, and they are still clicking on links, I’d like to advise them that they are, indeed blacklisted, thereby giving them the opportunity to get back on a list. As it stands now, someone who gets blacklisted by an admin because of any variety of reasons, doesn’t know they are blacklisted because links still work. So this could possibly recover some lost subscribers.
I don’t think any other bulk mailing system offers this and it could be useful.