@lucky_slevin Well I can’t do anything when the server responds with this message… I have just checked with our test account @posteo.de and there’s an invalid TLS certificate, but when accepting the certificate, everything works as expected.
You can try with your browser: open https://posteo.de:8443 in the (Desktop or mobile) browser and enter your credentials. When they’re accepted, you will see:
<d:error><s:exception>Sabre_DAV_Exception_NotImplemented</s:exception><s:message>GET is only implemented on File objects</s:message></d:error>
Otherwise, you’ll see the
What happens when you visit https://posteo.de:8443 with your browser (which one?) and enter your credentials?