Receive SparkPost inbound relay webhooks
Configure an inbound domain and relay webhook, then process incoming message content separately from outbound event webhooks.
Reviewed
SparkPost lists Inbound Domains and Relay Webhooks separately from its outgoing Event Webhooks. Use the receiving resources for new incoming mail; a transmission-delivery event does not contain a customer’s new reply.
Configure the inbound chain
- Confirm account/region support and follow the receiving resources linked in SparkPost’s API reference.
- Choose a dedicated receiving domain/subdomain and publish its prescribed DNS records.
- Associate the appropriate relay webhook target and implement the documented endpoint security and notification format.
- Preserve stable message/recipient identifiers and handle the actual message content/attachments according to the relay payload, not an outbound event schema.
Keep any configured authentication secret outside source control. Do not assume the provider uses MailKite’s signature or that every region has identical feature availability.
Test processing and replay
Send one controlled message to the original incoming address. Verify domain receipt, webhook dispatch, source authentication, and durable work before acknowledgement. Check batching and duplicate handling using safe test data.
If receipt works but forwarding fails, investigate target reachability/security and the relay webhook configuration. Avoid repeated DNS changes when the failure is downstream HTTP delivery.
Separate raw message storage from agent/tool execution and limit attachments. MailKite offers another receiving path with its own DNS, payload, and signature contract; a provider migration must change all three together.