Hi,
It is mentioned on your site that free version of eM Client has a limit of 2 accounts.
My question is the following: what do you mean by “2 accounts”? – 2 mailboxes or 2 (mail+calendar or mail+contacts).
Depends on the server. For example Google offer one account and you’ll get a primary CalDAV and CardDAV (calendar and contact). In such case, it 1 account. But if you have a CardDAV host on separate server eg. Funambol, or multi-calendar under Google (which requires you to setup addtional CalDAV account), than you’ll need extra account.