mail admins? Proposal of solution

[nuclearcat at nuclearcat.com (Denys Fedoryshchenko)]

On 2020-04-30 02:43, Mark Andrews wrote:
> And it is still on going.  Just got 4 of these.
> 
> Mark
> 
Technical proposal how to solve that.

At 1st of month send monthly reminder manually, to each subscriber, but 
encode recipient address in Reply-To: a bit special way.
First, you need catch-all alias on special domain.
Then, you calculate reply-to, for example if destination recipient:
hash("secret-keyword" + user at domain.com)=aabbccdd
So, it becomes:
Reply-To: aabbccdd at monthly.nanog.org

Then just check all bounces received to *@monthly.nanog.org, and 
unsubscribe relevant users.