We run a webhosting server - WHM, Cpanel but some other servers don`t accept emails form our server. We are not blacklisted and the reverse DNS is ok. But we may have an open relay. But we`re not sure.
1. How can we check it to be sure and how can we manage to NOT to have an open relay?
2. What other factors can cause that email from our mail server are not delivered to some destinations?
3. What can we do to have it in 100% state that it will always work well and every email will be delivered.
Thank you very much for help. Our server Ip is 22.214.171.124.