By default Exim will be using the main server shared IP address to send mails. If the main server IP is listed in any spam database, then we will not be able to send mails. In order to fix this, we can change the Exim mail server IP to any other secondary IP which is not blacklisted on the server.
1. Open the Exim configuration file
vi /etc/exim.conf
2. Locate the section of the file that contains the following:
remote_smtp:
driver = smtp
3. Replace this section with the following modified version :
remote_smtp:
driver = smtp
interface = <IP>
4. Restart Exim using the following commands
service exim restart
or
/etc/init.d/exim restart
This will change the outgoing mail server IP of the exim mail server.