Sorry, I did not answer “Did you enter an email address or base URL in DAVdroid?”.
I entered Base URL: https://al.emailarray.com/dav.php
That URL came from PolarisMail’s http://wiki.polarismail.com/display/Support/Sync+contacts+and+events+via+CalDAV+(iOS%2C+Android%2C+Thunderbird%2C+eM+Client)+-+Basic