Hi there,

I've been trying to setup org-caldav to sync to my owndrive calendar.

Setup is

#+begin_src emacs-lisp
(setq org-caldav-url "
https://my.owndrive.com/remote.php/caldav/calendars/myusername")
(setq org-caldav-calendar-id "myid")
(setq org-caldav-inbox "~/org/test.org")
#+end_src

When I try org-caldav-sync, it fails with:

Contacting host: my.owndrive.com:443
gnutls.c: [0] (Emacs) fatal error: Public key signature verification has
failed.
gnutls.el: (err=[-89] Public key signature verification has failed.) boot:
(:priority NORMAL :hostname my.owndrive.com :loglevel 0 :min-prime-bits 256
:trustfiles nil :crlfiles nil :keylist nil :verify-flags nil :verify-error
nil :callbacks nil)
edebug-signal: GnuTLS error: #<process my.owndrive.com>, -89

Testing this with gnutls on the command line confirms the problem:
% gnutls-cli -V -p 443 my.owndrive.com
...
- Status: The certificate is NOT trusted. The signature in the certificate
is invalid.
*** Verifying server certificate failed...
*** Fatal error: Error in the certificate.
*** Handshake has failed
GnuTLS error: Error in the certificate.

Does anyone know if there is a way to tell org-caldav or url-dav to use an
untrusted certificate?

Thanks,
  Seb