On shared hosting server’s you’ll probably find yourself blocked by other mail providers because of high mail volume or one of your users spamming. To change your exim IP for outgoing mail, you can edit your /etc/exim.conf file and locate this section:

remote_smtp:
driver = smtp

And below this add:

interface - xxx.xxx.xxx.xxx

Replace the x’s with the backup mail IP. Note that the backup mail IP needs to be added to the server, and should have a valid PTR and A-record.

Note:  On newer versions of cPanel where domainkeys are installed, you will need to add another interface line:

 dk_remote_smtp:
driver = smtp
dk_private_key = “/var/cpanel/domain_keys/private/${dk_domain}”
dk_canon = nofws
dk_selector = default
interface = xxx.xxx.xxx.xxx