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 smtplibaio import 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.

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.

import asyncio

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

from smtplibaio import SMTP_SSL


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 = str(Address("Alice", "alice", "example.org"))
    to_addr = str(Address("Bob", "bob", "example.net"))
    bcc_addr = str(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, bcc_addr]

    # Build the EmailMessage object:
    message = EmailMessage()
    message.add_header("From", from_addr)
    message.add_header("To", to_addr)
    message.add_header("Bcc", 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, 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() ;
• 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

• STARTTLS is not supported yet,
• 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.