It is a very common problem and a very disastrous as well, when your mail server ip get black listed then all of your email accounts belong to all of your clients are unable to send and receive emails.
First of all we will try to understand what a thing make a mail server’s ip black listed.
Basically there are two important things, about one most of people are well aware and about the second only few know.
1. Due to huge spam made by email accounts comes under a certain mail server
2. Due to no rDNS (reverse DNS) entry of main ip of your server.
What to do if a mail server ip is black listed.
First of all try to control the spamming if you find that you mail server ip is black listed due to spam.
Secondly ask you admin to configure rDNS against your host name (host name could be any domain name lies in that server), if you feel that mail server ip is black listed due to No Entry of rDNS.
But that process could take a bit time to settle things, what you can do to tackle things in that mean time, simply change the ip of the mail server from primary to one of the secondary ips which one is not black listed.
How you can change the IP of mail server?
You can updated Exim’s configuration with your request to have outbound mail sent over the IP: ***.***.***.*** (new ip) You could be able to accomplish this by WHM >> Exim Configuration Editor >> Domains and IPS and Enabling >> Reference /etc/mailips for outgoing SMTP connections
From there, You have to edit /etc/mailips to read the wild card (all domains) and update the IP referenced as shown below:
root@CL-T044-433CL [~]# cat /etc/mailips
*: (***.***.***.***) new ip