Errors & status codes - Inflection Help Center

Situation	Status	Code
Contact not found (by id or email)	`400`	`BAS-E-002`
List or email not found	`404`	`NOT_FOUND`
Duplicate list name	`409`	`LIST_ALREADY_EXISTS`
Duplicate email name	`409`	`TEMPLATE_ALREADY_EXISTS`
Request body fails validation	`400`	`VALIDATION_ERROR`, with a field detail such as `fromEmail._schema`
From-email domain not approved for the org	`400`	`UnapprovedEmailDomainException`
Removing an unknown contact from a list	`404`	`CONTACT_NOT_FOUND`
Rate limit exceeded	`429`	See Rate Limits

A missing contact returns 400, while a missing list or email returns 404. Handle both. Don’t assume a single not-found code across resources.

Errors inside a 200

Two cases return 200 and still carry an error signal. Check the body, not just the status:

Bulk member add with unknown ids: the valid ids are added, and the response’s errors[] array carries CONTACTS_NOT_FOUND for the ids that were skipped.
Unknown transaction id: GET /v1/contacts/transactions/{transactionId} returns 200 with status: NOT_EXIST instead of an HTTP error.

Pagination Rate Limits