I had reported the same thing in After update, all domains suddenly have the "autoconfig." and "autodiscover." subdomains added to them. I still don’t know why those domains where added in the first place. Is this a new behavior?
PS: Seems this was added in https://github.com/mail-in-a-box/mailinabox/pull/1467. AAAA records support will be added with https://github.com/mail-in-a-box/mailinabox/pull/1606.