Customize recipient email

Hi,
I would like to customize the content on the email when it is sent to the recipient. At present, after a user sends a message, they receive a copy of their message, along with a prepared message. I have searched your ‘Settings’ on the admin dashboard. I am able to change the heading of the email. But I am not able to change the content in the email itself. At present it says ‘Hello (user name),You are being contacted via (website name)’. And this is followed by details of the message that they sent. I would like to change the part that say ”Hello (user name),You are being contacted via (website name)’. How can I do that, please? Thank you!