eM Client has a default security feature that allows you to protect it with a password. This feature is especially great if you often use a shared computer at the office, home, or anywhere. By protecting the eM Client app with a password, no one can use it but you or those you have shared the password with.
To start protecting eM Client with a password, launch the eM Client app on your computer. Click menu and select Tools -> Settings.

Click the Password Protection option under the General block. Tick the Use password protected startup option and type your preferred password on the Password field and the Confirm password field to confirm it. Click the OK button to apply the password.

Restart your eM Client app (close and relaunch). From now on, you should be prompted to enter a password every time you launch eM Client on your computer.
eM Client itself is a great desktop-based email client app for business use. In addition to opening and sending emails, you can also use it to manage calendars and tasks. It is available for Windows and Mac. You will need a license key to use eM Client (you can use eM Client for free for personal use).