I got an email “Let’s Encrypt Subscriber Agreement Update” from firstname.lastname@example.org.
It didn’t tell me how to unsubscribe. I don’t even know the list name,
but it said “Dear let’s encrypt subscriber”, so the logical conclusion is that I’m subscribed to this list for life, and I’ll call it the “subscriber list” since I don’t know if has any official name.
I got subscribed when I did some initial testing. Subsequently, I don’t give my email when I register a domain, (I don’t want my email to be associated with each domain I register). But I do want to be on the “subscriber list” to get announcements (at least for now), but I don’t see any way to independently subscribe to this list, or any information about it at all when I google let’s encrypt mailing lists and browse the first 2 pages. You support registering domains without email addresses, then you should logically support people registering to your “subscriber list” outside of the registration process.