---
id: aiosmtplib
version: "5.1.2"
license: MIT
license_treatment: permissive
maintenance: active
---

# aiosmtplib — asyncio SMTP client

License: permissive · Maintenance: active · Downloads: 19.6M/mo

## What it is and what it does

aiosmtplib is a pure-Python SMTP client built for asyncio that lets you send email without blocking your event loop. Unlike the standard library's synchronous smtplib, it integrates directly into async/await code, making it suitable for applications that handle many concurrent operations—web servers, task queues, or any asyncio-based system that needs to send mail.

The package has no runtime dependencies and installs as a single wheel. It wraps the SMTP protocol in async methods, so you construct an EmailMessage using the standard library's email.message module, then pass it to aiosmtplib.send() or manage a connection manually. Requires Python 3.10 or later.

Use it for:

- Send transactional emails from a FastAPI or Starlette web application without blocking request handlers
- Batch email delivery in an asyncio task queue or background job system
- Integrate email notifications into an async event-driven architecture
- Concurrent mail operations where multiple messages are sent in parallel within a single event loop

## Worth the install?

AI-flagged interpretation of the facts above — verify before relying.

aiosmtplib is an asynchronous SMTP client that sends email messages using asyncio, allowing non-blocking email operations in async Python applications.

Yes. aiosmtplib is actively maintained, has no dependencies, carries a permissive MIT license, and fills a clear gap for async Python applications that need SMTP. The low install friction and stable production status make it a straightforward choice if you're already using asyncio and need to send email without blocking.

## Install

pip install aiosmtplib
uv add aiosmtplib
poetry add aiosmtplib

## Installing aiosmtplib

Before you install: Low install friction with no runtime dependencies. Active maintenance: last commit 2026-08-06, release 55 days ago. Stable production status since first release in 2016.

License in practice: MIT license permits commercial and private use with minimal restrictions; you may use, modify, and distribute aiosmtplib freely provided you retain the license notice.

Quickstart:

import asyncio
from email.message import EmailMessage
import aiosmtplib

message = EmailMessage()
message["From"] = "root@localhost"
message["To"] = "somebody@example.com"
message["Subject"] = "Hello World!"
message.set_content("Sent via aiosmtplib")

asyncio.run(aiosmtplib.send(message, hostname="127.0.0.1", port=25))

Requires Python 3.10 or later.

Verify before relying:

- Whether TLS/SSL support is included and how to configure it
- Authentication method support (PLAIN, LOGIN, etc.) and configuration
- Connection pooling or session management capabilities

## Package facts

- License: MIT (permissive)
- Python support: supports_current
- Install friction: low
- Maintenance: active
- Downloads: 19.6M/month (top 5,000 on PyPI)
- Known vulnerabilities: none known

## Tags

async smtp client, asyncio email sending, non-blocking smtp, python async mail, asyncio email library, async-io, email-delivery

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