These are settings you need to change in Windows.
On Windows 11, go to Windows Settings > Apps > Default Apps. Find the eM Client entry and click on it. Scroll down to the MAILTO option and change it to eM Client.
On Windows 10, go to Windows Settings > Apps > Default Apps. Scroll down to Set defaults by app. Click on eM Client and choose Manage. Change the MAILTO option to eM Client.
