How do I set up email for the primary domain from a subdomain?

Ok. So I got this working and most things seem to be working. What I have:

Results:

Remaining problems: I can’t seem to view mailman archives for example.com. It seems to be going to eg (for a list named devops) https://example.com/pipermail/devops/

I looked in /etc/mailman/mm_cfg.py and couldn’t see a setting to change the webhost to emailbox.example.com? (The urls already had emailbox.example.com) Would you know where the correct setting for mailman is? I looked around on google but didn’t immediately see anything. (there was some talk of using something like:

./withlist -l -r fix_url list_name --urlhost=host2.domain.com

But that is list by list and not all the lists freshly created in the future, etc…