Attaching Files to a Draft

Attachments must be bound to an existing draft. First create the draft, then create a separate upload session for each attachment and upload the file stream.

Call Sequence

1. Create a draft and obtain message.id.
2. Call Create Attachment Upload Session.
3. Use the upload URL or session identifier in the response to call Upload File Stream.
4. Once all attachments are complete, send the draft or keep it in the drafts folder for manual confirmation.

Python Example

from pathlib import Path
import requests

API_BASE = "https://alimail-cn.aliyuncs.com"


def upload_attachment(
    access_token: str,
    mailbox: str,
    draft_id: str,
    file_path: Path,
) -> None:
    headers = {
        "Authorization": f"Bearer {access_token}",
        "Content-Type": "application/json",
    }
    session = requests.post(
        f"{API_BASE}/v2/users/{mailbox}/messages/{draft_id}/attachments/createUploadSession",
        headers=headers,
        json={"attachment": {"name": file_path.name, "isInline": False}},
        timeout=15,
    )
    session.raise_for_status()
    upload_url = session.json()["uploadUrl"]

    with file_path.open("rb") as stream:
        uploaded = requests.post(
            upload_url,
            headers={"Authorization": f"Bearer {access_token}"},
            data=stream,
            timeout=60,
        )
    uploaded.raise_for_status()

Before uploading, validate the file size, extension, and content type. Do not log the upload URL, as it may contain session information that is valid for a short period.

Reference: Original Example.