> ## Documentation Index
> Fetch the complete documentation index at: https://sendmux.ai/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Create a mailbox API key

> Mints an additional bearer token plus IMAP/SMTP mailbox password for an existing mailbox. The plaintext key and password are shown exactly once — store them immediately.

Supply an `Idempotency-Key` header (any unique string, max 255 chars) to safely retry on network errors. Replays with the same key return the original response; replays with a different body return `409 idempotency_conflict`.



## OpenAPI

````yaml /openapi-app.json post /mailboxes/{public_id}/keys
openapi: 3.1.0
info:
  description: Programmatic access to your Sendmux email infrastructure.
  title: Sendmux API
  version: 1.0.0
servers:
  - description: API v1
    url: https://app.sendmux.ai/api/v1
security:
  - bearerAuth: []
paths:
  /mailboxes/{public_id}/keys:
    post:
      tags:
        - Mailboxes
      summary: Create a mailbox API key
      description: >-
        Mints an additional bearer token plus IMAP/SMTP mailbox password for an
        existing mailbox. The plaintext key and password are shown exactly once
        — store them immediately.


        Supply an `Idempotency-Key` header (any unique string, max 255 chars) to
        safely retry on network errors. Replays with the same key return the
        original response; replays with a different body return `409
        idempotency_conflict`.
      operationId: managementCreateMailboxKey
      parameters:
        - in: path
          name: public_id
          required: true
          schema:
            description: Mailbox public ID
            type: string
        - in: header
          name: Idempotency-Key
          required: false
          schema:
            description: >-
              Client-chosen unique key to safely retry the request. Cached for
              24h per (team, endpoint, key). Different body with same key
              returns 409 idempotency_conflict.
            example: mailbox-keys-create-20260424-001
            maxLength: 255
            type: string
      requestBody:
        content:
          application/json:
            schema:
              additionalProperties: false
              properties:
                app_name:
                  description: Human-friendly label for the new API key.
                  maxLength: 255
                  minLength: 1
                  type: string
              required:
                - app_name
              type: object
      responses:
        '201':
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/MailboxAppPasswordResultResponse'
          description: >-
            Mailbox API key created. The response carries a `Location` header
            pointing at the canonical URL for the new key.
          headers:
            Location:
              description: Canonical URL for the newly created API key.
              schema:
                example: >-
                  /api/v1/mailboxes/mx_clxxxxxxxxxxxxxxxxxxxxxxxxx/keys/smx_clxxxxxxxxxxxxxxxxxxxxxxxxx
                type: string
        '400':
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ApiError'
          description: Invalid request body
        '404':
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ApiError'
          description: Mailbox not found
        '409':
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ApiError'
          description: >-
            Credential limit reached (`limit_exceeded`) or idempotency key
            conflict (`idempotency_conflict`).
        '413':
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ApiError'
          description: Request body too large
        '422':
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ApiError'
          description: Mailbox is not active
        '503':
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ApiError'
          description: Credential setup temporarily unavailable
      security:
        - bearerAuth: []
components:
  schemas:
    MailboxAppPasswordResultResponse:
      allOf:
        - $ref: '#/components/schemas/SuccessEnvelope'
        - properties:
            data:
              $ref: '#/components/schemas/MailboxAppPasswordResult'
            meta:
              $ref: '#/components/schemas/ResponseMeta'
          required:
            - data
          type: object
      unevaluatedProperties: false
    ApiError:
      additionalProperties: false
      properties:
        error:
          additionalProperties: false
          properties:
            code:
              description: Machine-readable error code
              enum:
                - invalid_parameter
                - missing_parameter
                - authentication_required
                - insufficient_permissions
                - not_found
                - conflict
                - limit_exceeded
                - idempotency_conflict
                - payload_too_large
                - validation_error
                - rate_limit_exceeded
                - service_unavailable
                - internal_error
              example: invalid_parameter
              type: string
            doc_url:
              description: Link to relevant documentation
              type: string
            errors:
              description: >-
                Accumulated per-field issues for validation errors. Only present
                on 400/422 responses.
              items:
                $ref: '#/components/schemas/ApiErrorDetail'
              type: array
            message:
              description: Human-readable error description
              type: string
            param:
              description: The parameter that caused the error
              type: string
            retryable:
              description: >-
                Whether the caller may safely retry this request. 4xx are
                typically false (except 429); 5xx are typically true.
              example: false
              type: boolean
          required:
            - code
            - message
            - retryable
          type: object
        meta:
          additionalProperties: false
          properties:
            request_id:
              example: req_clxxxxxxxxxxxxxxxxxxxxxxxxx
              type: string
          required:
            - request_id
          type: object
        ok:
          enum:
            - false
          type: boolean
      required:
        - ok
        - error
        - meta
      type: object
    SuccessEnvelope:
      properties:
        meta:
          additionalProperties: {}
          properties: {}
          type: object
        ok:
          enum:
            - true
          type: boolean
      required:
        - ok
        - meta
      type: object
    MailboxAppPasswordResult:
      additionalProperties: false
      properties:
        credential:
          allOf:
            - $ref: '#/components/schemas/MailboxCredential'
            - type: object
      required:
        - credential
      type: object
    ResponseMeta:
      additionalProperties: false
      properties:
        request_id:
          example: req_clxxxxxxxxxxxxxxxxxxxxxxxxx
          type: string
      required:
        - request_id
      type: object
    ApiErrorDetail:
      additionalProperties: false
      properties:
        code:
          description: >-
            Machine-readable issue code from the validator (e.g. zod issue
            code).
          example: invalid_string
          type: string
        field:
          description: Dot-path of the offending request field.
          example: recipient.email
          type: string
        message:
          description: Human-readable issue description.
          type: string
      required:
        - field
        - code
        - message
      type: object
    MailboxCredential:
      additionalProperties: false
      description: >-
        Initial credential for the mailbox. `null` if credential generation
        failed — call POST /mailboxes/{id}/keys to retry.
      properties:
        imap_port:
          description: IMAP retrieval port
          example: 993
          type: integer
        key_prefix:
          type: string
        key_suffix:
          type: string
        public_id:
          description: Credential public ID
          example: smx_clxxxxxxxxxxxxxxxxxxxxxxxxx
          type: string
        secret:
          description: >-
            Mailbox credential — shown exactly once. Use as a Bearer token on
            the HTTP API and as the password for IMAP retrieval and SMTP
            submission.
          type: string
        server:
          description: Mailbox server name
          example: mail.sendmux.ai
          type: string
        smtp_port:
          description: SMTP submission port
          example: 587
          type: integer
        username:
          description: Mailbox email address used as the login
          type: string
      required:
        - public_id
        - secret
        - key_prefix
        - key_suffix
        - server
        - imap_port
        - smtp_port
        - username
      type:
        - object
        - 'null'
  securitySchemes:
    bearerAuth:
      bearerFormat: API Key
      description: >-
        Sendmux API key. Use a root API key for Management API routes, or a
        mailbox credential for Mailbox API routes. Obtain keys from the
        dashboard under API Keys.
      scheme: bearer
      type: http

````