Allowlist the IP addresses Plain sends requests from - Plain Docs

Plain sends webhooks, customer card requests, and workflow HTTP requests from fixed IP addresses, one set per region. Allowlist the addresses for your workspace’s region at your firewall or API gateway so your endpoint only accepts these requests from Plain.

IP addresses for the UK region

For workspaces in Plain’s UK region, hosted in AWS eu-west-2 (London), Plain sends requests from these addresses. Allow all of them, since any request can come from any address in the list:

175.75.250
43.212.141
41.120.118

Other requests Plain makes, such as fetching knowledge sources or calling MCP servers, come from addresses Plain doesn’t publish.

Keep verifying requests from Plain

Every workspace in a region sends from the same addresses, so anyone can point their own webhook target at your URL and pass the allowlist. Keep verifying requests with request signing or mTLS: the allowlist adds to them and doesn’t replace them.