Sync2em - carddav and caldav settings

Greetings, the current eM Client 4.0 Pro I have in three machines has became unusable as it does not show a number of messages. The answer I had from Softmaker technical support is that “Actually the problem lies on Microsoft Exchange - there is a bug in MIME encoding and unfortunately, we cannot provide you any solution at the moment.”. As the other clients show the messages correctly, with great regret I’ll have to abandon eM. I am currently experimenting with Thunderbird, using a CardDAV client for sync2em. The contact list shows all right but there is no way to make the calendar and task functions work together. I have the calendar only or nothing. Could you please advise?