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OpenIndex uses Resend-backed email infrastructure to handle both outbound conversation email and inbound email routing. To receive inbound email on a custom domain (e.g. support.example.com), you provision a receiving domain and a webhook through the admin API.

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Prerequisites

Set the following environment variables before provisioning:
  • AUTH_RESEND_KEY — your Resend API key
  • RESEND_WEBHOOK_SECRET — webhook signing secret from Resend
See environment variables for details on each variable.

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Setup steps

1

Get email provider info

Check the current provider status before provisioning:
GET /admin/external/email/provider
Authorization: Bearer <admin-pat>
This returns the Resend account details and current provisioning state associated with your deployment.
2

Provision a receiving domain

Create a new receiving domain. OpenIndex will provision the domain in Resend and return DNS records for you to add to your DNS provider.
POST /admin/external/email/domains/provision
Authorization: Bearer <admin-pat>
Content-Type: application/json

{
  "name": "support.example.com"
}
The response includes the domain ID and any DNS records required for verification.Via CLI:
oi settings external email domains provision --name support.example.com
3

Add DNS records

Add the DNS records returned in the provisioning response to your DNS provider. Records typically include MX and TXT entries for the subdomain.DNS propagation can take up to 48 hours, though it usually completes within a few minutes.
4

Verify the domain

Once DNS records are in place, trigger verification:
POST /admin/external/email/domains/:id/verify
Authorization: Bearer <admin-pat>
Resend will check the DNS records and confirm the domain is ready to receive email.
5

Provision an inbound webhook

Set up the inbound webhook so Resend forwards received email to your OpenIndex deployment:
POST /admin/external/email/webhooks/provision
Authorization: Bearer <admin-pat>
OpenIndex registers the webhook endpoint (POST /webhooks/resend/email-received) with Resend and stores the webhook configuration.

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Managing existing resources

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Refresh domain or webhook state

If your Resend state becomes out of sync, refresh it to pull the latest status: 
POST /admin/external/email/domains/:id/refresh
Authorization: Bearer <admin-pat>

POST /admin/external/email/webhooks/:id/refresh
Authorization: Bearer <admin-pat>

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List provisioned resources

# List all provisioned receiving domains
GET /admin/external/email/domains
Authorization: Bearer <admin-pat>

# List all provisioned webhooks
GET /admin/external/email/webhooks
Authorization: Bearer <admin-pat>

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Delete a domain

Deleting a receiving domain stops email delivery for that domain. Any mailboxes routing to the domain will stop receiving inbound messages.
DELETE /admin/external/email/domains/:id
Authorization: Bearer <admin-pat>

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How inbound email flows

Once your domain and webhook are provisioned:
  1. An email arrives at an address on your receiving domain (e.g. support@support.example.com).
  2. Resend forwards the email to POST /webhooks/resend/email-received on your deployment.
  3. OpenIndex verifies the payload signature using RESEND_WEBHOOK_SECRET.
  4. The email is normalized into a conversation and matched to a work item based on your mailbox routing rules.
See the Email API reference for how to configure mailboxes and routing rules.