YouTube. Send & receive messages
Google says "As of July 9, 2018, the ability to send, receive, or read private messages in Creator Studio is no longer available." BUT....
To email someone YouTuber using the Business Inquiry Email:
- Go to the YouTube Channel you want to email.
- Select the About tab of their channel.
- If a Business Inquiry Email is provided, select “View Email Address”. If you don’t see a Business Inquiry Email, that means that the channel owner didn’t provide one.
- Use the email to send a message to the channel.