Seems to be working now (latest DAVdroid version). We will add mail.ru to our list of tested services.
POLL: New option in DAVdroid 1.0: Limit sync to X days into the past – what should be the default value?
DAVdroid 1.0 – which will be our first official stable release – will have a new option to significantly increase performance. You’ll have the ability to limit the sync process to a given number of days into the past. Help us to decide what we should set as a standards value by taking the poll. Thank you!
For now, we will use 90 days as default value.