I keep getting the message “An error has occurred in the applicaiton that prevents it from continuing. The The application will terminate.” When I press “continue” it checks the database and data and then goes back to the same message, and there seems no way out of the loop. I think the problem may be connected with an email, but I cannot delete the email because this loop always intervenes.
One thing you can try is to rename the database directory, and then when eM Client restarts it will be with a blank database. That will determine if the problem is with the application or the data.
To do that on Windows, with eM Client closed, rename the C:\Users\yourusername\AppData\Roaming\eM Client\ folder. You may have to enable hidden items in Explorer to get there.
Then restart eM Client and see what happens.