:mod:`smtplib` --- SMTP protocol client

The :mod:`smtplib` module defines an SMTP client session object that can be used to send mail to any Internet machine with an SMTP or ESMTP listener daemon. For details of SMTP and ESMTP operation, consult RFC 821 (Simple Mail Transfer Protocol) and RFC 1869 (SMTP Service Extensions).

A :class:`SMTP` instance encapsulates an SMTP connection. It has methods that support a full repertoire of SMTP and ESMTP operations. If the optional host and port parameters are given, the SMTP :meth:`connect` method is called with those parameters during initialization. An :exc:`SMTPConnectError` is raised if the specified host doesn't respond correctly. The optional timeout parameter specifies a timeout in seconds for blocking operations like the connection attempt (if not specified, the global default timeout setting will be used).

For normal use, you should only require the initialization/connect, :meth:`sendmail`, and :meth:`quit` methods. An example is included below.

A :class:`SMTP_SSL` instance behaves exactly the same as instances of :class:`SMTP`. :class:`SMTP_SSL` should be used for situations where SSL is required from the beginning of the connection and using :meth:`starttls` is not appropriate. If host is not specified, the local host is used. If port is zero, the standard SMTP-over-SSL port (465) is used. keyfile and certfile are also optional, and can contain a PEM formatted private key and certificate chain file for the SSL connection. The optional timeout parameter specifies a timeout in seconds for blocking operations like the connection attempt (if not specified, the global default timeout setting will be used).

The LMTP protocol, which is very similar to ESMTP, is heavily based on the standard SMTP client. It's common to use Unix sockets for LMTP, so our :meth:`connect` method must support that as well as a regular host:port server. To specify a Unix socket, you must use an absolute path for host, starting with a '/'.

Authentication is supported, using the regular SMTP mechanism. When using a Unix socket, LMTP generally don't support or require any authentication, but your mileage might vary.

A nice selection of exceptions is defined as well:

SMTP Objects

An :class:`SMTP` instance has the following methods:

Low-level methods corresponding to the standard SMTP/ESMTP commands HELP, RSET, NOOP, MAIL, RCPT, and DATA are also supported. Normally these do not need to be called directly, so they are not documented here. For details, consult the module code.

SMTP Example

This example prompts the user for addresses needed in the message envelope ('To' and 'From' addresses), and the message to be delivered. Note that the headers to be included with the message must be included in the message as entered; this example doesn't do any processing of the RFC 822 headers. In particular, the 'To' and 'From' addresses must be included in the message headers explicitly.

import smtplib

def prompt(prompt):
    return input(prompt).strip()

fromaddr = prompt("From: ")
toaddrs  = prompt("To: ").split()
print("Enter message, end with ^D (Unix) or ^Z (Windows):")

# Add the From: and To: headers at the start!
msg = ("From: %s\r\nTo: %s\r\n\r\n"
       % (fromaddr, ", ".join(toaddrs)))
while True:
    try:
        line = input()
    except EOFError:
        break
    if not line:
        break
    msg = msg + line

print("Message length is", len(msg))

server = smtplib.SMTP('localhost')
server.set_debuglevel(1)
server.sendmail(fromaddr, toaddrs, msg)
server.quit()