I’m using a regular server release of NC-19 (mariaDB, nginx) together with SSL certificates for my-own-dyndns-domain.org from Let’s Encrypt. Everything works great, including the Thunderbird calendar via CALDAV. On my fritzbox I set up nat loopback (at least I think that the adding the domain name my-own-dyndns-domain.org in the section “DNS-Rebind-Protection” does that). Once, I’m in my local network, the domain address my-own-dyndns-domain.org is forwarded to the local (http) IP of the server – great. However, thunderbird complains about the let’s encrypt certificate. I do understand this, because the local IP is different from the one to which the dyndns address is bound.
Could anyone point me into the direction of how I can still use the caldav calendar when I’m in the same network as my server is? Do I need a second certificate?