See support eM Client documentation.
“How to move my eM Client data to a new computer?”
Also see @Gary post from the following thread.
https://forum.emclient.com/t/move-em-client-from-an-old-to-a-new-computer/70831
The best way to ensure all your data and settings are brought over is through Backup and Restore.
On computer A:
Create a backup using Menu > File > Backup.
Deactivate your license if you are no longer going to use eM Client on this device in Menu > Help > License.
Find the .ZIP backup file and move it to computer B (default in …\Documents\eM Client).
On computer B:
Install eM Client (https://www.emclient.com/release-history)
Skip initial setup.
Restore from your backup through Menu > File > Restore. If you put the backup file in this device in the same folder structure as the default (…\Documents\eM Client) the restore will find it right away, otherwise, you’ll need to specify the path where the backup file can be found.
Activate your license in Menu > Help > License. If you have lost your license activation key, you can have it resent to you from this page.