mailcue 0.1.3

Official Python SDK for MailCue — open-source email testing and production server.

MailCue Python SDK

Official Python client for MailCue — the open-source email testing and production server (Postfix + Dovecot + FastAPI + React) packaged as one Docker container.

The SDK is the same in dev and prod: point it at http://localhost:8088 while you build, then swap base_url to your production MailCue deployment when you ship.

Install

pip install mailcue

Requires Python 3.9+.

Quick start: send an email

from mailcue import Mailcue

client = Mailcue(api_key="mc_xxx")  # base_url defaults to http://localhost:8088

result = client.emails.send(
    from_="[e-mail]",
    to=["[e-mail]"],
    subject="Welcome",
    html="<h1>Hi there</h1>",
)
print(result.message_id)

Need async? Use AsyncMailcue — same surface, all methods become coroutines:

import asyncio
from mailcue import AsyncMailcue

async def main() -> None:
    async with AsyncMailcue(api_key="mc_xxx") as client:
        await client.emails.send(
            from_="[e-mail]",
            to=["[e-mail]"],
            subject="Welcome",
            html="<h1>Hi there</h1>",
        )

asyncio.run(main())

Listing an inbox

inbox = client.emails.list(mailbox="[e-mail]", page_size=20)
for email in inbox.emails:
    print(email.uid, email.subject, email.from_address)

detail = client.emails.get(inbox.emails[0].uid, mailbox="[e-mail]")
print(detail.text_body)

Waiting for an email (CI)

wait_for polls a mailbox until matching messages arrive, or raises mailcue.TimeoutError after timeout seconds. Filters (subject, from_address, to_address) are case-insensitive substrings on top of the server-side search.

found = client.emails.wait_for(
    mailbox="[e-mail]",
    subject="Welcome",
    timeout=10,
)
assert len(found) == 1

Attachments

attachments accepts raw bytes, str, or a pathlib.Path. The SDK base64-encodes the content for you.

from pathlib import Path

client.emails.send(
    from_="[e-mail]",
    to=["[e-mail]"],
    subject="Invoice",
    html="<p>See attached.</p>",
    attachments=[
        {
            "filename": "invoice.pdf",
            "content_type": "application/pdf",
            "content": Path("./invoice.pdf"),
        }
    ],
)

Real-time events (SSE)

for event in client.events.stream():
    print(event.event_type, event.data)

The async version:

async with AsyncMailcue(api_key="mc_xxx") as client:
    async for event in client.events.stream():
        print(event.event_type, event.data)

The SSE client auto-reconnects with exponential backoff if the connection drops.

Error handling

from mailcue import (
    Mailcue,
    AuthenticationError,
    NotFoundError,
    RateLimitError,
    ValidationError,
)

client = Mailcue(api_key="mc_xxx")

try:
    client.emails.get("not-a-real-uid", mailbox="[e-mail]")
except NotFoundError as exc:
    print("missing:", exc)
except RateLimitError as exc:
    print(f"slow down; retry after {exc.retry_after}s")
except AuthenticationError:
    print("bad API key")
except ValidationError as exc:
    print("server rejected the request:", exc.detail)

Configuration

client = Mailcue(
    api_key="mc_xxx",                        # or bearer_token="eyJ..."
    base_url="https://mail.example.com",     # default: http://localhost:8088
    timeout=30.0,                            # seconds
    max_retries=3,                           # 502/503/504 + network errors
    verify=True,                             # set False for self-signed dev TLS
)

You can also inject your own httpx.Client / httpx.AsyncClient via http_client= for advanced cases (custom transports, proxies, mTLS).

Resources

Resource	Methods
client.emails	send, list, get, get_raw, get_attachment, delete, inject, bulk_inject
client.mailboxes	list, create, delete, stats, purge, list_emails
client.domains	list, create, get, verify_dns, delete
client.aliases	list, create, get, update, delete
client.gpg	list, generate, get, export_public, import_key, publish, delete
client.api_keys	list, create, delete
client.system	health, get_certificate, download_certificate, settings, tls_status
client.events	stream() (SSE iterator)

License

MIT — see LICENSE.

Project home: https://github.com/Olib-AI/mailcue