Zendesk
Zendesk publishes main public ingress and egress IP addresses as JSON. Poll the feed on a schedule — ranges can change without a fixed cadence. Product-specific and mail-server IPs may require additional sources.
Autonomous systems
AS21880
AS61186
Published ranges
Zendesk public ingress & egress IPs
Official feedJSON of main Zendesk ingress and egress CIDRs used for firewall configuration.