Hi,
First of all, Erik, thank you for mustering the energy to take care of this migration and inventorying of the lists. Does anyone volunteer to be part of a Mailing Lists Working Committee which can make a point of periodically inventorying and auditing these lists for spam, active moderators, etc? You would get all the technical support you need.
I note that some of these are still very much active projects but they've scattered elsewhere over the years, for example cl-pdf hosts their code at github and appears to communicate pretty much exclusively through github Issues. Even some active projects hosted at our own gitlab may be communicating through gitlab Issues or other means and thus not register any mailing list traffic through our mailman.
Anyway, if none of a particular project's mailing lists have been active in several years, then it's difficult to make any case for keeping said list active, in the face of the overhead costs Erik mentions, especially if they can be re-activated easily when needed. However, in the Common Lisp space-time continuum, five years is not all that long. I'd be curious what the numbers look like if you go back eight or even 10 years?
Erik, did you say that you sent verification emails to the list owners of these lists? Is the list owner by definition the only moderator, or can they assign other moderators? As I understand it, we can detect non-responsive moderators by seeing mails bounce to an admin account, is that right? If so, how can volunteers sign up to be privvy to those bounced mails and perhaps help to mitigate? Is that just another list to sign up for through the mailman3 web page?
One other question for Erik - are these active lists and archives publicly crawl-able? Because that brings up the whole question of what is CLF's position on serving up for free such content, which is under the stewardship of clnet infrastructure, to all comers, including the slew of neural net training hoovers which now apparently a permanent feature of life online. But that's a discussion for a different thread.