I don’t like eM Client 7. How do I go back to eM Client 6?
Unfortunately the databases are incompatible, so you will not be able to use the same one. You could export any data you want to keep that is not synced via IMAP or Exchange, then close eM Client and delete C:\Users_username_\AppData\Roaming\eM Client. Uninstall version 7, then install version 6 and import your data.