The IP Address whitelist is important to have enabled, to prevent potential attacks to your server. It allows only MageMail servers to access the MageMail API.
The IP Address should be enabled by default but if for some reason it’s not enabled, here’s how you can enable it.
In the Magento backend top navigation, under Promotions, go to MageMail Connector.
Under MageMail Advanced Settings, make sure that Enable IP Address Whitelist is set to Yes and that Whitelisted IP Addresses contains the IP: [please login]
X-Forwarded-For
If your site is behind a load balancer or reverse proxy, you may need to enable the Use X-Forwarded-For setting. It tells the IP address whitelist to look at the HTTP-X-Forwarded-For header instead of the REMOTE_ADDR header.
