Assist you in importing your self-signed certificate to your Android device: After you enter the host name of your HTTPS site, its certificate will be extracted and shown to you. Possible mistakes that may prevent successful import will be detected and displayed. As soon as you have verified the certificate by its details and fingerprints, it will be exported into a .crt file. You can then simply import the certificate from the file with a few clicks. When the certificate was imported correctly, it will be accepted in (nearly) all apps, including https://f-droid.org/packages/at.bitfire.davdroid and the Android email app don't choose "Accept all certificates" there, see <a href="https://code.google.com/p/android/issues/detail?id=67038">https://code.google.com/p/android/issues/detail?id=67038</a>.