How can I change the default media player on eM Client from Windows Media Player to VLC Player?

Change default media player.

Good morning,
as far as I know a file is opened via the file association: Opening certain types of files with certain programs.

To open a file by double-clicking always with a specific program, change the default application for this file type. To do this, in the settings under System/Standard Apps at the bottom of the screen, click Select standard apps by file type. A long list shows all file types stored in the registry. Here you assign the desired standard app to each file type. - For example: Mp4 file with VLC Player.
This should allow eMClient to open the file with the desired app.

The option is also there in VLC itself. Preferences > File Extensions Associations. Just tick Select All.

Thank you Huber & Gary for your very prompt replies. Works a treat!