text: Hello admins, The server will start to send the Spam mails due to malicious code or compromised mail box. In that case, our outgoing IP address will get blocked by several spam filters including Gmail and other mail services.
  In this case, we have to wait for a long time to get whitelisted or have to pay to be whitelisted. But if you have secondary IP addresses for your server, we can do this trick to send emails and let the main IP to whitelist automatically.
  Important: Before proceeding with this, make sure that you have fixed the compromised code or application or mailbox. Else, your secondary IP address will also get blocked on Spam filters.
  If no ‘src’ listed in ‘ip’ output for the default route, then the main IP on the interface is used for outgoing connections. You can change it using: