I/O error: Cannot verify hostname: caldav.hostpoint.ch

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I was using Davdroid with caldav/carddav successfully for few months. Since about two weeks i have synchronization problems. My provider hostpoint.ch is running Open-Xchange. They say that they didn’t change the configuration. Server is available via web browser.

The error message is following: I/O error: Cannot verify hostname: caldav.hostpoint.ch
I’m using version 0.6.2 from f-droid repository.
Server: https://caldav.hostpoint.ch
Configuration from my provider: https://support.hostpoint.ch/index.php?page=ArticleShortListPage&navigation=23&category=103

Here is the log output:
I/davdroid.QueryServerDialogFragment(19945): onCreateLoader
D/davdroid.DavHttpClient(19945): Disabling compression for debugging purposes
D/davdroid.DavHttpClient(19945): Logging network traffic for debugging purposes
D/davdroid.WebDavResource(19945): Using preemptive authentication (not compatible with Digest auth)
D/davdroid.SNISocketFactory(19945): Preparing direct SSL connection (without proxy) to https://caldav.hostpoint.ch:443
D/davdroid.SNISocketFactory(19945): Using documented SNI with host name caldav.hostpoint.ch
E/GpsXtraDownloader( 837): No XTRA servers were specified in the GPS configuration

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I’m using CyanogenMod 11-20140803. Android version 4.4.4
Privacy Guard is not enabled for Davdroid

[rfc2822]

As you can see in the Qualys SSL Test for caldav.hostpoint.ch, the certificate chain is incomplete. Please ask your provider (hostpoint.ch) to include the intermediate certificate “GeoTrust SSL CA” in the server’s SSL configuration as it’s not included in Android, maybe referencing this issue report.