Mailbox threads

The Sendmux Mailbox API is for mailbox-scoped access. Use it when a client should act as a mailbox, or as one mailbox from a connected-app mailbox set, without managing team-wide resources.

Thread APIs

Use thread endpoints when you need conversation-level context without fetching every body.

List threads

curl "https://app.sendmux.ai/api/v1/mailbox/threads?q=invoice&participant=sender@example.com&folder_id=inbox&is_unread=true&limit=10" \
  -H "Authorization: Bearer smx_mbx_your_key_here"

{
  "ok": true,
  "data": [
    {
      "id": "thr_123",
      "subject": "Invoice question",
      "message_count": 2,
      "unread_count": 1,
      "has_attachments": true,
      "folder_ids": ["inbox"],
      "participants": [
        { "email": "sender@example.com", "name": "Sender" },
        { "email": "agent@example.com", "name": "Agent" }
      ],
      "last_message": {
        "id": "msg_456",
        "thread_id": "thr_123",
        "subject": "Re: Invoice question",
        "preview": "Thanks, I found it.",
        "has_attachments": false
      },
      "states": {
        "thread_state": "thread_state_token",
        "email_state": "message_state_token"
      }
    }
  ],
  "pagination": {
    "has_more": false
  },
  "meta": {
    "request_id": "req_clxxxxxxxxxxxxxxxxxxxxxxxxx",
    "query_state": "thread_query_state_token"
  }
}

Thread list filters:

Parameter	Purpose
`q`	Search common address, subject, and body text.
`participant`	Match sender or recipient addresses.
`folder_id`	Restrict results to one folder.
`is_unread`	Match unread or read threads.
`has_attachment`	Match threads with or without attachment metadata.
`after`	Match threads with messages at or after this time.
`before`	Match threads with messages before this time.
`cursor`	Continue from a previous page.
`limit`	Return `1` to `100` threads.
`sort_direction`	Sort by most recent message, `desc` or `asc`.

Read a thread

curl https://app.sendmux.ai/api/v1/mailbox/threads/thr_123 \
  -H "Authorization: Bearer smx_mbx_your_key_here"

The response includes the same thread metadata as the list endpoint plus message_ids in chronological order. Use GET /mailbox/threads/{thread_id}/messages for paginated message summaries, or GET /mailbox/threads/{thread_id}/content when you need cleaned bodies.

Getting started

Developer tools

AI integrations

Sending

Receiving

Domains

Monitoring

Webhooks

Use cases

Integrations

Account and billing

Mailbox threads

Thread APIs

List threads

Read a thread

Next steps

Mailbox API introduction

Search and batch operations

​Thread APIs

​List threads

​Read a thread

​Next steps

Mailbox API introduction

Search and batch operations

Thread APIs

List threads

Read a thread

Next steps