How can I force Exim to send emails through another server?

Question

linux

Hello!
There are several backend servers and one frontend.
PHP is now installed on the backend servers, which sends letters directly to users with the mail () function.
I would like these emails to be sent through the frontend server in order to hide the ip addresses of the backend servers.
Is it possible to solve this problem only with Exim on the frontend and backend servers?
Maybe on the frontend you can configure it as a proxy for the backend?
Thank you.

Answer 1

Considering that the entire route of its passage gets into the letter, such a scheme will not hide anything.
And you can specify the route, manualroute

Answer 2

So you can
http://my-mails.ru/hide-received-mailing-script/