Load Postmark data to DuckDB

Postmark is an email delivery service that provides a REST API for sending transactional emails, managing domains, and accessing server-level data. Everything needed to build a working Postmark → DuckDB pipeline is on this page: the API's base URL, authentication, endpoints, pagination and incremental field — plus a prompt that hands the whole job to your coding agent.

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Build your Postmark to DuckDB pipeline

Paste this prompt into Claude, Codex, or Cursor. The agent does the rest.

PromptCopy prompt
Run uvx dlthub-init@latest to build a pipeline from Postmark to DuckDB and run it on dltHub

That scaffolds a dltHub workspace and installs the dltHub AI harness — the project rules, the secrets-management skill, and the dlt MCP server your agent needs to work safely. From there it reads the Postmark API, proposes the endpoints to load, then writes, runs and validates the pipeline while you review rather than type. Credentials are inspected through MCP tools, so your agent never reads secrets.toml itself. How the LLM-native workflow works →

Prefer to write it yourself? Every fact the agent uses is below.

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Postmark API at a glance

These values come from the Postmark API reference — the authoritative source if anything here looks out of date.

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How do I authenticate with the Postmark API?

Postmark API authentication requires providing an API token via specific HTTP headers, either 'X-Postmark-Server-Token' for server-level privileges or 'X-Postmark-Account-Token' for account-level privileges. Both the header name and value are case-insensitive.

1. Get your credentials

To obtain your API credentials, log in to your Postmark account. For server-level actions (e.g., sending emails, searching messages), navigate to your specific Server, then click the 'API Tokens' tab to copy your Server API token. For account-level actions (e.g., managing servers or domains), navigate to your account settings and locate the Account API token in the 'API Tokens' tab. Always treat these tokens as sensitive credentials.

2. Add them to .dlt/secrets.toml

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[sources.postmark_source]
server_token = "your_server_api_token_here"
account_token = "your_account_api_token_here"

dlt reads this file automatically at runtime. With the harness, the setup-secrets skill prompts you for the values and never handles the raw credential in chat. For production, see setting up credentials with dlt.

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What Postmark data can I load into DuckDB?

These are the Postmark endpoints dlt can load into DuckDB:

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How do I load only new Postmark records?

The Postmark API reference does not document a timestamp or sequence field for these endpoints, so there is nothing to advertise here as verified. Pick a field from the endpoints table above that increases with every write, then set it as the cursor_path.

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{"name": "outbound_messages", "endpoint": {
    "path": "messages/outbound",
    # Replace with a field that increases on every write.
    "incremental": {"cursor_path": "REPLACE_ME", "initial_value": "2024-01-01T00:00:00Z"},
}}

On the first run dlt loads everything from initial_value; on every run after that it requests only what changed and appends with write_disposition="merge" if you set a primary key. See incremental loading.

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What does the generated Postmark pipeline look like?

A standard dlt REST API pipeline — the same code you would write by hand, loading servers and email from the Postmark API into DuckDB:

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import dlt
from dlt.sources.rest_api import RESTAPIConfig, rest_api_resources

@dlt.source
def postmark_source(api_token=dlt.secrets.value):
    config: RESTAPIConfig = {
        "client": {
            "base_url": "https://api.postmarkapp.com",
            "auth": {"type": "api_key", "api_key": api_token, "name": "X-Postmark-Server-Token or X-Postmark-Account-Token", "location": "header"},
        },
        "resources": [
            {"name": "outbound_messages", "endpoint": {"path": "messages/outbound", "data_selector": "Messages"}},
            {"name": "inbound_messages", "endpoint": {"path": "messages/inbound", "data_selector": "InboundMessages"}}
        ],
    }
    yield from rest_api_resources(config)


def load_postmark_to_duckdb() -> None:
    pipeline = dlt.pipeline(
        pipeline_name="postmark_pipeline",
        destination="duckdb",
        dataset_name="postmark_data",
    )
    load_info = pipeline.run(postmark_source())
    print(load_info)


if __name__ == "__main__":
    load_postmark_to_duckdb()

Run it with python postmark_pipeline.py. The agent iterates on this until it loads cleanly — you review and approve, rather than write it from scratch.

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How do I query Postmark data in DuckDB?

dlt creates one table per resource. Query the loaded data with Python or SQL — or ask your agent to, through the MCP server's execute_sql_query tool.

Python (pandas DataFrame):

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import dlt

data = dlt.pipeline("postmark_pipeline").dataset()
df = data.outbound_messages.df()
print(df.head())

SQL:

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SELECT * FROM postmark_data.outbound_messages LIMIT 10;

See querying your data with dataset and exploring it in marimo notebooks.

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How do I deploy the Postmark to DuckDB pipeline in production?

The pipeline runs locally, which is ideal for prototyping and one-off analysis. When you need it on a schedule, monitored on every load, and shared with your team, deploy the same dlt code on the dltHub platform — no infrastructure to maintain. The prompt above already ends with "run it on dltHub", so your agent can take it there directly.

• Deploy & schedule — run the pipeline as a managed job with automatic retries.
• Monitor — observable job queues, alerting, and load metrics for every run.
• Transform — promote raw Postmark loads into governed, documented models.
• Visualize & share — explore data in notebooks and publish live dashboards instead of static screenshots.

Book a demo →

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What other destinations can I load Postmark data to?

dlt loads into any of these — only the destination argument changes:

Set dlt.pipeline(destination="snowflake") and add credentials in .dlt/secrets.toml. On the dltHub platform the same pipeline runs against a managed Iceberg lakehouse. See the full destinations list.

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Next steps

• Ready for production? Book a demo of the dltHub platform →
• dlt LLM-native workflow docs
• REST API source reference
• Join the dlt community on Slack