Setting up exim4 on Debian 9. How to close open relay?

Question

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Hello! Set up mail in a bunch of exim4 with dovecot. Everything is going fine, but I decided to check the queue and saw 19 thousand letters. I started to understand and scanned my domain here https://emailsecuritygrader.com/
It turns out that my server is open for forwarding (open relay)
I am new to this topic. Tell me how to close open relay?

Answer 1

and eat a pound of salt