Email notification customisation

Hi,

I would like to change the notification that user get by email when they have a new message.


In this notification, there is the name of the person that sent the message and and extract of the message content.


I would like to remove the extract content so they don't know what the message is about before coming to the site.


I would like alos to remove the name of the sender so they discover it also when on the site.


Where can i change these please?


Thank you for your help.

regards