CAdroid

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
https://code.google.com/p/android/issues/detail?id=67038.