Whitelisting by IP is not recommended. The Cloud Elements platform is a public cloud hosted by AWS, and shared IPs may change without notice; accordingly, the recipient would be whitelisting all traffic from Cloud Elements.
If you plan on using endpoints that need Cloud Elements 2.0 IPs to be whitelisted, all IPs for the given environment need to be whitelisted. For example, if you are using both a staging and a US production environment, then all the IPs for these environments need to be whitelisted, but EU production IPs would not. This is because we cannot guarantee which IPs will actually be in use by our servers; accordingly, all IPs must be whitelisted.
If whitelisting by IP is the only option, the recipient domain will want to check for the most up-to-date IP information by downloading our ip-ranges file. This file will be updated whenever new IPs are added to Cloud Elements' IP range. If a receiving server is whitelisting the range, it's recommended they periodically check to ensure they have the current range. To be notified when new IPs are added to the list, navigate to Best Practices, and click the Subscribe button.
Note: to make sure your category subscriptions make it to your inbox, you may need to add our release notes email address (firstname.lastname@example.org) to a list of safe senders.