> ## Documentation Index > Fetch the complete documentation index at: https://inbound.new/docs/llms.txt > Use this file to discover all available pages before exploring further. # Add a message to a folder > Requires a read_write mailbox. Stores a message in a folder, like IMAP APPEND: either a raw RFC 822 message (base64) or message fields that are built into one (for example a draft). Nothing is sent. Size and storage limits are the same as over IMAP. Appending to Sent with a Message-ID that is already there returns the existing message. ## OpenAPI ````yaml https://inbound.new/openapi.json post /api/e2/mailboxes/{id}/folders/{folder}/messages openapi: 3.1.0 info: title: Inbound Email API description: >+ # Inbound API The Inbound API allows you to manage email infrastructure programmatically - domains, email addresses, webhooks, and more. ## Authentication All API requests require a Bearer token in the Authorization header: ```bash curl -H "Authorization: Bearer YOUR_API_KEY" \ https://inbound.new/api/e2/domains ``` ## Base URL ``` https://inbound.new/api/e2 ``` ## Quick Start 1. **Create a domain** - Register your domain with Inbound 2. **Configure DNS** - Add the provided DNS records to your domain 3. **Create an email address** - Set up addresses to receive emails 4. **Create an endpoint** - Configure where emails are delivered (webhook, forwarding, etc.) version: 2.0.0 servers: - url: https://inbound.new description: Production API server security: - bearerAuth: [] tags: - name: Webhooks description: Webhooks sent by Inbound to your configured endpoints when events occur. - name: Emails description: >- Send, list, and manage emails. Supports immediate sending, scheduling, replies, and retry functionality. - name: Mail description: >- Inbox and thread views for received emails. Filter by domain, address, or search. - name: Domains description: >- Manage domains for sending and receiving emails. Domains must be verified via DNS before use. - name: Endpoints description: >- Configure where incoming emails are delivered - webhooks, email forwarding, or custom handlers. - name: Email Addresses description: Create and manage email addresses on your verified domains. - name: Attachments description: Download email attachments using authenticated requests. paths: /api/e2/mailboxes/{id}/folders/{folder}/messages: post: tags: - Mailboxes summary: Add a message to a folder description: >- Requires a read_write mailbox. Stores a message in a folder, like IMAP APPEND: either a raw RFC 822 message (base64) or message fields that are built into one (for example a draft). Nothing is sent. Size and storage limits are the same as over IMAP. Appending to Sent with a Message-ID that is already there returns the existing message. operationId: postApiE2MailboxesByIdFoldersByFolderMessages parameters: - name: id in: path required: true schema: type: string - name: folder in: path required: true schema: type: string requestBody: required: true content: application/json: schema: type: object properties: raw: maxLength: 1402200 description: >- The full RFC 822 message, base64-encoded. The decoded message must be valid UTF-8 (7-bit or UTF-8 headers and bodies); encode other 8-bit content with base64 or quoted-printable. type: string from: maxLength: 512 description: Defaults to the mailbox's sending identity or login address type: string to: anyOf: - maxLength: 4096 type: string - maxItems: 100 type: array items: maxLength: 512 type: string cc: anyOf: - maxLength: 4096 type: string - maxItems: 100 type: array items: maxLength: 512 type: string replyTo: anyOf: - maxLength: 4096 type: string - maxItems: 100 type: array items: maxLength: 512 type: string subject: maxLength: 998 type: string text: type: string html: type: string headers: type: object patternProperties: ^(.*)$: type: string inReplyTo: maxLength: 998 type: string references: maxItems: 100 type: array items: maxLength: 998 type: string flags: maxItems: 50 description: >- Defaults to none for raw messages, and to \Seen (plus \Draft in Drafts) for message fields type: array items: maxLength: 255 type: string date: description: Internal date (ISO 8601); defaults to now type: string application/x-www-form-urlencoded: schema: type: object properties: raw: maxLength: 1402200 description: >- The full RFC 822 message, base64-encoded. The decoded message must be valid UTF-8 (7-bit or UTF-8 headers and bodies); encode other 8-bit content with base64 or quoted-printable. type: string from: maxLength: 512 description: Defaults to the mailbox's sending identity or login address type: string to: anyOf: - maxLength: 4096 type: string - maxItems: 100 type: array items: maxLength: 512 type: string cc: anyOf: - maxLength: 4096 type: string - maxItems: 100 type: array items: maxLength: 512 type: string replyTo: anyOf: - maxLength: 4096 type: string - maxItems: 100 type: array items: maxLength: 512 type: string subject: maxLength: 998 type: string text: type: string html: type: string headers: type: object patternProperties: ^(.*)$: type: string inReplyTo: maxLength: 998 type: string references: maxItems: 100 type: array items: maxLength: 998 type: string flags: maxItems: 50 description: >- Defaults to none for raw messages, and to \Seen (plus \Draft in Drafts) for message fields type: array items: maxLength: 255 type: string date: description: Internal date (ISO 8601); defaults to now type: string multipart/form-data: schema: type: object properties: raw: maxLength: 1402200 description: >- The full RFC 822 message, base64-encoded. The decoded message must be valid UTF-8 (7-bit or UTF-8 headers and bodies); encode other 8-bit content with base64 or quoted-printable. type: string from: maxLength: 512 description: Defaults to the mailbox's sending identity or login address type: string to: anyOf: - maxLength: 4096 type: string - maxItems: 100 type: array items: maxLength: 512 type: string cc: anyOf: - maxLength: 4096 type: string - maxItems: 100 type: array items: maxLength: 512 type: string replyTo: anyOf: - maxLength: 4096 type: string - maxItems: 100 type: array items: maxLength: 512 type: string subject: maxLength: 998 type: string text: type: string html: type: string headers: type: object patternProperties: ^(.*)$: type: string inReplyTo: maxLength: 998 type: string references: maxItems: 100 type: array items: maxLength: 998 type: string flags: maxItems: 50 description: >- Defaults to none for raw messages, and to \Seen (plus \Draft in Drafts) for message fields type: array items: maxLength: 255 type: string date: description: Internal date (ISO 8601); defaults to now type: string responses: '201': description: Response for status 201 content: application/json: schema: type: object properties: folder: type: string uid: type: number uidValidity: type: number required: - folder - uid - uidValidity '400': description: Response for status 400 content: application/json: schema: type: object properties: error: type: string required: - error '401': description: Response for status 401 content: application/json: schema: type: object properties: error: type: string required: - error '403': description: Response for status 403 content: application/json: schema: type: object properties: error: type: string required: - error '404': description: Response for status 404 content: application/json: schema: type: object properties: error: type: string required: - error '409': description: Response for status 409 content: application/json: schema: type: object properties: error: type: string required: - error '413': description: Response for status 413 content: application/json: schema: type: object properties: error: type: string required: - error components: securitySchemes: bearerAuth: type: http scheme: bearer bearerFormat: API Key description: >- Your Inbound API key. Include it in the Authorization header as: Bearer ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.