Thunderbird Calendar and Adressbook Sync not working

Dear forum,

I am following the steps described here (except installing the lightning calendar):

Although I already added an exception for the SSL certificate of my Nextcloud server, I keep getting the errors below when trying to add the CalDAV / CardDAV account. Can anybody let me know what I am doing wrong?


Screenshot from 2022-04-15 20-31-58

You’ll want to check that thunderbird add-on documentation and any related github repo.

Also please fill this out and edit into your post so we can better help you:

Hi @Geronimo2021

Are you using the IP address to connect to your server? Im not an expert but I suspect you have to use a Fully Qualified Domain Name (FQDN) in order for it to work with HTTPS. Problems with self-signed certificate · Issue #261 · jobisoft/DAV-4-TbSync · GitHub

You haven’t provided enough information, especially about your self signed certificate.

The error message explicitly states you need to import the cert into Thunderbird - have you done that? You only state you’ve “added an exception for the SSL certificate of my Nextcloud server”. It’s not clear if you mean your browser has an exception for your Nextcloud, or if you actually added the cert to Thunderbird.

Also, is your self signed cert for an IP address or for a domain name? It matter which you’ve chosen.

Lastly, you really need to understand how certificates work. SSL certificates are fundamentally broken, the protocol was last updated in 1996, and was officially depreciated in 2015. Chances are you’re using a TLS certificate, but generated by OpenSSL?

It also matters how your webserver is configured, it’s possible you’ve followed internet instructions that use ciphers that Thunderbird doesn’t understand. Or maybe you’re using TLS 1.0 or 1.1, which Thunderbird no longer supports. (Or even worse, maybe you really are using SSL!)

By not filling out the support template, you’ve made it very difficult for us to help you.

Edit: I just noticed the URL you’re using to connect to CalDav. It contains “.well-known”. That’s REALLY wrong. Are you using a self signed certificate? Or are you using Let’s Encrypt? Jesus dude, the lack of information in your post is frustrating. Let’s Encrypt uses the “.well-known” token to update a certificate.

Your CalDav link should look more like:

Next time, PLEASE complete the support template.