Server Side Tags with CardDav?

With V.9 the server side contact tags work great in Google accounts but not with the Mailenable CardDav server.

Are server side tags supported on CardDav servers at all or is this a Mailenable deficiency?

By the way: heads up für your Version 9. I am really impressed by the plethora of features and the user friendlyness of this wonderful mail client.

It looks like according to this page the Server-side tags are only supported for Gmail and Exchange/Office 365 accounts.