smtplibaio

The smtplibaio package provides an SMTP client session object that can be used to send e-mail in an asynchronous way (i.e. using asyncio).

Examples

Let's start with a very basic example, using SMTP_SSL:

import asyncio
from email.headerregistry import Address
from email.message import EmailMessage

from smtplibaio import SMTP, SMTP_SSL


async def send_email():
    from_addr = "bob@example.net"
    to_addr = "alice@example.org"

    message = "Hi Alice !"

    async with SMTP_SSL() as client:
        await client.sendmail(from_addr, to_addr, message)


if __name__ == '__main__':
    loop = asyncio.get_event_loop()
    loop.run_until_complete(send_email())
    loop.close()

As you can see, the Asynchronous Context Manager makes it really easy to use.

STARTTLS is supported only if you have the aioopenssl module installed. You must tell SMTP to use it upon instantiation:

async def send_email():
    """
    """
    from_addr = "bob@example.net"
    to_addr = "alice@example.org"

    message = "Hi Alice !"

    async with SMTP(use_aioopenssl=True) as client:
    await client.starttls()
        await client.sendmail(from_addr, to_addr, message)


if __name__ == '__main__':
    loop = asyncio.get_event_loop()
    loop.run_until_complete(send_email())
    loop.close()

In the next example, we are specifying the server hostname and port, we are using authentication and we are using the objects provided by the email package available in the Python Standard Library (i.e. email.message.EmailMessage) to build a proper email message.

async def send_email():
    # SMTP server:
    smtp_server = "smtp.example.org"
    port = 587

    # Credentials used to authenticate:
    username = "alice"
    passwd = "5ecreT!"

    # Use of Address object is not mandatory:
    from_addr = Address("Alice", "alice", "example.org")
    to_addr = Address("Bob", "bob", "example.net")
    bcc_addr = Address("John", "john", "example.net")

    # E-mail subject and content:
    subject = "Testing smtplibaio"
    content = "Look, all emails sent from this method are BCCed to John !"

    # Build the list of recipients (To + Bcc):
    recipients = [to_addr.addr_spec, bcc_addr.addr_spec]

    # Build the EmailMessage object:
    message = EmailMessage()
    message.add_header("From", str(from_addr))
    message.add_header("To", str(to_addr))
    message.add_header("Bcc", str(bcc_addr))
    message.add_header("Subject", subject)
    message.add_header("Content-type", "text/plain", charset="utf-8")
    message.set_content(content)

    # Send the e-mail:
    async with SMTP_SSL(hostname=smtp_server, port=port) as client:
        await client.auth(username, passwd)
        await client.sendmail(from_addr.addr_spec, recipients, message.as_string())


if __name__ == "__main__":
    loop = asyncio.get_event_loop()
    loop.run_until_complete(send_email())
    loop.close()

You can also have a more fine-grained control using the lower-level methods.

Supported SMTP commands

• EHLO - SMTP.ehlo() ;
• HELO - SMTP.helo() ;
• STARTTLS - SMTP.starttls() (depending on aioopenssl availability) ;
• AUTH - SMTP.auth() (LOGIN, PLAIN and CRAM-MD5 mechanisms are suported) ;
• MAIL FROM - SMTP.mail() ;
• RCPT TO - SMTP.rcpt() ;
• VRFY - SMTP.vrfy() ;
• DATA - SMTP.data() ;
• EXPN - SMTP.expn() ;
• NOOP - SMTP.noop() ;
• QUIT - SMTP.quit() ;
• HELP - SMTP.help().

Current limitations

• There is no direct support for Python's email.message.EmailMessage. You can still use email.message.EmailMessage.as_string() or str(email.message.EmailMessage) instead. See the example above for further details.

How to contribute

We use black, isort in combination with pre-commit to ensure one coding style and reduce the risk of merge conflicts. Please [install pre-commit] to ensure your commits also meet these standards. When you see something to improve, have ideas for better tests or documentation, please create issues or create a pull request.