Zendesk maintains this list of public IP addresses to allow customers to provide whitelist rules for access to their internal resources by Zendesk servers.
This is not a definitive source, and addresses will change over time as Zendesk expands into new localities. As some of these changes reflect a change in strategy, there might not be advance notice when changes are made. Zendesk highly recommends that customers use some kind of authentication mechanism to determine whether inbound/outbound requests are valid, rather than using IP address.
LAST UPDATED: 2016-07-05
Note: There may, from time-to-time, be new IP addresses added or removed. We will strive to keep this document updated with those changes, though it may be operationally necessary to add new IP addresses.
Need help? As this list may change from time to time, we invite you to submit a ticket to firstname.lastname@example.org with any questions, comments, or concerns about new addresses that may not be documented here.
Outbound Email Servers are listed in our spf record, which we update as needed.
Our spf record can be read by these commands:
host -t TXT mail.zendesk.com
dig txt mail.zendesk.com