How to hide server IP address in mail headers?

Question

Mail server

There is a website and it is hidden behind cloudflare in order to protect against DDOS attacks
. Outgoing mail from the site had to be forwarded through another mail server to hide the real IP address of the server, but the IP in the FROM field is stored in the mail headers.
Initial data - postfix mail server, nginx + php-fpm web server

Answer 1

On the destination mail server, you need to cut the headers where the IP of the real web server is specified.
Create a file /etc/postfix/anon-headers.pcre with the contents

/^User-Agent:/ IGNORE
/^X-Mailer:/ IGNORE
/^X-Originating-IP:/ IGNORE
/^Received:/ IGNORE

Add to the config /etc/postfix/main.cf anywhere
Restart postfix
systemctl restart postfix

Answer 2

To protect the site, you need to allow web traffic only from the white list (cloudflare + your own)
Cloudflare IP list: https://www.cloudflare.com/ips-v4