smtplib —-SMTP协议客户端

Source code:Lib/smtplib.py

The smtplib module defines an SMTP client session object that can be usedto send mail to any Internet machine with an SMTP or ESMTP listener daemon. Fordetails of SMTP and ESMTP operation, consult RFC 821 (Simple Mail TransferProtocol) and RFC 1869 (SMTP Service Extensions).

  • class smtplib.SMTP(host='', port=0, local_hostname=None, [timeout, ]source_address=None)
  • An SMTP instance encapsulates an SMTP connection. It has methodsthat support a full repertoire of SMTP and ESMTP operations. If the optionalhost and port parameters are given, the SMTP connect() method iscalled with those parameters during initialization. If specified,local_hostname is used as the FQDN of the local host in the HELO/EHLOcommand. Otherwise, the local hostname is found usingsocket.getfqdn(). If the connect() call returns anything otherthan a success code, an SMTPConnectError is raised. The optionaltimeout parameter specifies a timeout in seconds for blocking operationslike the connection attempt (if not specified, the global default timeoutsetting will be used). If the timeout expires, socket.timeout israised. The optional source_address parameter allows bindingto some specific source address in a machine with multiple networkinterfaces, and/or to some specific source TCP port. It takes a 2-tuple(host, port), for the socket to bind to as its source address beforeconnecting. If omitted (or if host or port are '' and/or 0 respectively)the OS default behavior will be used.

For normal use, you should only require the initialization/connect,sendmail(), and SMTP.quit() methods.An example is included below.

The SMTP class supports the with statement. When usedlike this, the SMTP QUIT command is issued automatically when thewith statement exits. E.g.:

  1. >>> from smtplib import SMTP
  2. >>> with SMTP("domain.org") as smtp:
  3. ...     smtp.noop()
  4. ...
  5. (250, b'Ok')
  6. >>>

在 3.3 版更改: 支持了 with 语句。

在 3.3 版更改: source_address argument was added.

3.5 新版功能: The SMTPUTF8 extension (RFC 6531) is now supported.

  • class smtplib.SMTPSSL(_host='', port=0, local_hostname=None, keyfile=None, certfile=None, [timeout, ]context=None, source_address=None)
  • An SMTP_SSL instance behaves exactly the same as instances ofSMTP. SMTP_SSL should be used for situations where SSL isrequired from the beginning of the connection and using starttls() isnot appropriate. If host is not specified, the local host is used. Ifport is zero, the standard SMTP-over-SSL port (465) is used. The optionalarguments local_hostname, timeout and source_address have the samemeaning as they do in the SMTP class. context, also optional,can contain a SSLContext and allows configuring variousaspects of the secure connection. Please read Security considerations forbest practices.

keyfile and certfile are a legacy alternative to context, and canpoint to a PEM formatted private key and certificate chain file for theSSL connection.

在 3.3 版更改: 增加了 context。

在 3.3 版更改: source_address argument was added.

在 3.4 版更改: The class now supports hostname check withssl.SSLContext.check_hostname and Server Name Indication (seessl.HAS_SNI).

3.6 版后已移除: keyfile and certfile are deprecated in favor of context.Please use ssl.SSLContext.load_cert_chain() instead, or letssl.create_default_context() select the system's trusted CAcertificates for you.

  • class smtplib.LMTP(host='', port=LMTP_PORT, local_hostname=None, source_address=None)
  • The LMTP protocol, which is very similar to ESMTP, is heavily based on thestandard SMTP client. It's common to use Unix sockets for LMTP, so ourconnect() method must support that as well as a regular host:portserver. The optional arguments localhostname and source_address have thesame meaning as they do in the SMTP class. To specify a Unixsocket, you must use an absolute path for _host, starting with a '/'.

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

A nice selection of exceptions is defined as well:

  • exception smtplib.SMTPException
  • Subclass of OSError that is the base exception class for allthe other exceptions provided by this module.

在 3.4 版更改: SMTPException became subclass of OSError

  • exception smtplib.SMTPServerDisconnected
  • This exception is raised when the server unexpectedly disconnects, or when anattempt is made to use the SMTP instance before connecting it to aserver.
  • exception smtplib.SMTPResponseException
  • Base class for all exceptions that include an SMTP error code. These exceptionsare generated in some instances when the SMTP server returns an error code. Theerror code is stored in the smtp_code attribute of the error, and thesmtp_error attribute is set to the error message.
  • exception smtplib.SMTPSenderRefused
  • Sender address refused. In addition to the attributes set by on allSMTPResponseException exceptions, this sets 'sender' to the string thatthe SMTP server refused.
  • exception smtplib.SMTPRecipientsRefused
  • All recipient addresses refused. The errors for each recipient are accessiblethrough the attribute recipients, which is a dictionary of exactly thesame sort as SMTP.sendmail() returns.
  • exception smtplib.SMTPDataError
  • The SMTP server refused to accept the message data.
  • exception smtplib.SMTPConnectError
  • Error occurred during establishment of a connection with the server.
  • exception smtplib.SMTPHeloError
  • The server refused our HELO message.
  • exception smtplib.SMTPNotSupportedError
  • The command or option attempted is not supported by the server.

3.5 新版功能.

  • exception smtplib.SMTPAuthenticationError
  • SMTP authentication went wrong. Most probably the server didn't accept theusername/password combination provided.

参见

  • RFC 821 - Simple Mail Transfer Protocol

  • Protocol definition for SMTP. This document covers the model, operatingprocedure, and protocol details for SMTP.

  • RFC 1869 - SMTP Service Extensions

  • Definition of the ESMTP extensions for SMTP. This describes a framework forextending SMTP with new commands, supporting dynamic discovery of the commandsprovided by the server, and defines a few additional commands.

SMTP Objects

An SMTP instance has the following methods:

  • SMTP.setdebuglevel(_level)
  • Set the debug output level. A value of 1 or True for level results indebug messages for connection and for all messages sent to and received fromthe server. A value of 2 for level results in these messages beingtimestamped.

在 3.5 版更改: Added debuglevel 2.

  • SMTP.docmd(cmd, args='')
  • Send a command cmd to the server. The optional argument args is simplyconcatenated to the command, separated by a space.

This returns a 2-tuple composed of a numeric response code and the actualresponse line (multiline responses are joined into one long line.)

In normal operation it should not be necessary to call this method explicitly.It is used to implement other methods and may be useful for testing privateextensions.

If the connection to the server is lost while waiting for the reply,SMTPServerDisconnected will be raised.

  • SMTP.connect(host='localhost', port=0)
  • Connect to a host on a given port. The defaults are to connect to the localhost at the standard SMTP port (25). If the hostname ends with a colon (':')followed by a number, that suffix will be stripped off and the numberinterpreted as the port number to use. This method is automatically invoked bythe constructor if a host is specified during instantiation. Returns a2-tuple of the response code and message sent by the server in itsconnection response.
  • SMTP.helo(name='')
  • Identify yourself to the SMTP server using HELO. The hostname argumentdefaults to the fully qualified domain name of the local host.The message returned by the server is stored as the helo_resp attributeof the object.

In normal operation it should not be necessary to call this method explicitly.It will be implicitly called by the sendmail() when necessary.

  • SMTP.ehlo(name='')
  • Identify yourself to an ESMTP server using EHLO. The hostname argumentdefaults to the fully qualified domain name of the local host. Examine theresponse for ESMTP option and store them for use by has_extn().Also sets several informational attributes: the message returned bythe server is stored as the ehlo_resp attribute, does_esmtpis set to true or false depending on whether the server supports ESMTP, andesmtp_features will be a dictionary containing the names of theSMTP service extensions this server supports, and their parameters (if any).

Unless you wish to use has_extn() before sending mail, it should not benecessary to call this method explicitly. It will be implicitly called bysendmail() when necessary.

  • SMTP.ehlo_or_helo_if_needed()

  • This method calls ehlo() and/or helo() if there has been noprevious EHLO or HELO command this session. It tries ESMTP EHLOfirst.

    • SMTPHeloError
    • The server didn't reply properly to the HELO greeting.
  • SMTP.hasextn(_name)
  • Return True if name is in the set of SMTP service extensions returnedby the server, False otherwise. Case is ignored.
  • SMTP.verify(address)
  • Check the validity of an address on this server using SMTP VRFY. Returns atuple consisting of code 250 and a full RFC 822 address (including humanname) if the user address is valid. Otherwise returns an SMTP error code of 400or greater and an error string.

注解

Many sites disable SMTP VRFY in order to foil spammers.

  • SMTP.login(user, password, *, initial_response_ok=True)

  • Log in on an SMTP server that requires authentication. The arguments are theusername and the password to authenticate with. If there has been no previousEHLO or HELO command this session, this method tries ESMTP EHLOfirst. This method will return normally if the authentication was successful, ormay raise the following exceptions:

Each of the authentication methods supported by smtplib are tried inturn if they are advertised as supported by the server. See auth()for a list of supported authentication methods. initial_response_ok ispassed through to auth().

Optional keyword argument initial_response_ok specifies whether, forauthentication methods that support it, an "initial response" as specifiedin RFC 4954 can be sent along with the AUTH command, rather thanrequiring a challenge/response.

在 3.5 版更改: SMTPNotSupportedError may be raised, and theinitial_response_ok parameter was added.

  • SMTP.auth(mechanism, authobject, *, initial_response_ok=True)
  • Issue an SMTP AUTH command for the specified authenticationmechanism, and handle the challenge response via authobject.

mechanism specifies which authentication mechanism is tobe used as argument to the AUTH command; the valid values arethose listed in the auth element of esmtp_features.

authobject must be a callable object taking an optional single argument:

data = authobject(challenge=None)

If optional keyword argument initial_response_ok is true,authobject() will be called first with no argument. It can return theRFC 4954 "initial response" ASCII str which will be encoded and sent withthe AUTH command as below. If the authobject() does not support aninitial response (e.g. because it requires a challenge), it should returnNone when called with challenge=None. If initial_response_ok isfalse, then authobject() will not be called first with None.

If the initial response check returns None, or if initial_response_ok isfalse, authobject() will be called to process the server's challengeresponse; the challenge argument it is passed will be a bytes. Itshould return ASCII str data that will be base64 encoded and sent to theserver.

The SMTP class provides authobjects for the CRAM-MD5, PLAIN,and LOGIN mechanisms; they are named SMTP.auth_cram_md5,SMTP.auth_plain, and SMTP.auth_login respectively. They all requirethat the user and password properties of the SMTP instance areset to appropriate values.

User code does not normally need to call auth directly, but can insteadcall the login() method, which will try each of the above mechanismsin turn, in the order listed. auth is exposed to facilitate theimplementation of authentication methods not (or not yet) supporteddirectly by smtplib.

3.5 新版功能.

  • SMTP.starttls(keyfile=None, certfile=None, context=None)
  • Put the SMTP connection in TLS (Transport Layer Security) mode. All SMTPcommands that follow will be encrypted. You should then call ehlo()again.

If keyfile and certfile are provided, they are used to create anssl.SSLContext.

Optional context parameter is an ssl.SSLContext object; This isan alternative to using a keyfile and a certfile and if specified bothkeyfile and certfile should be None.

If there has been no previous EHLO or HELO command this session,this method tries ESMTP EHLO first.

3.6 版后已移除: keyfile and certfile are deprecated in favor of context.Please use ssl.SSLContext.load_cert_chain() instead, or letssl.create_default_context() select the system's trusted CAcertificates for you.

在 3.3 版更改: 增加了 context。

在 3.4 版更改: The method now supports hostname check withSSLContext.checkhostname and _Server Name Indicator (seeHAS_SNI).

在 3.5 版更改: The error raised for lack of STARTTLS support is now theSMTPNotSupportedError subclass instead of the baseSMTPException.

  • SMTP.sendmail(from_addr, to_addrs, msg, mail_options=(), rcpt_options=())
  • Send mail. The required arguments are an RFC 822 from-address string, a listof RFC 822 to-address strings (a bare string will be treated as a list with 1address), and a message string. The caller may pass a list of ESMTP options(such as 8bitmime) to be used in MAIL FROM commands as mail_options.ESMTP options (such as DSN commands) that should be used with all RCPTcommands can be passed as rcpt_options. (If you need to use different ESMTPoptions to different recipients you have to use the low-level methods such asmail(), rcpt() and data() to send the message.)

注解

The from_addr and to_addrs parameters are used to construct the messageenvelope used by the transport agents. sendmail does not modify themessage headers in any way.

msg may be a string containing characters in the ASCII range, or a bytestring. A string is encoded to bytes using the ascii codec, and lone \rand \n characters are converted to \r\n characters. A byte string isnot modified.

If there has been no previous EHLO or HELO command this session, thismethod tries ESMTP EHLO first. If the server does ESMTP, message size andeach of the specified options will be passed to it (if the option is in thefeature set the server advertises). If EHLO fails, HELO will be triedand ESMTP options suppressed.

This method will return normally if the mail is accepted for at least onerecipient. Otherwise it will raise an exception. That is, if this method doesnot raise an exception, then someone should get your mail. If this method doesnot raise an exception, it returns a dictionary, with one entry for eachrecipient that was refused. Each entry contains a tuple of the SMTP error codeand the accompanying error message sent by the server.

If SMTPUTF8 is included in mail_options, and the server supports it,from_addr and to_addrs may contain non-ASCII characters.

This method may raise the following exceptions:

  • SMTPRecipientsRefused

  • All recipients were refused. Nobody got the mail. The recipientsattribute of the exception object is a dictionary with information about therefused recipients (like the one returned when at least one recipient wasaccepted).

  • SMTPHeloError

  • The server didn't reply properly to the HELO greeting.

  • SMTPSenderRefused

  • The server didn't accept the from_addr.

  • SMTPDataError

  • The server replied with an unexpected error code (other than a refusal of arecipient).

  • SMTPNotSupportedError

  • SMTPUTF8 was given in the mail_options but is not supported by theserver.

Unless otherwise noted, the connection will be open even after an exception israised.

在 3.2 版更改: msg may be a byte string.

在 3.5 版更改: SMTPUTF8 support added, and SMTPNotSupportedError may beraised if SMTPUTF8 is specified but the server does not support it.

  • SMTP.sendmessage(_msg, from_addr=None, to_addrs=None, mail_options=(), rcpt_options=())
  • This is a convenience method for calling sendmail() with the messagerepresented by an email.message.Message object. The arguments havethe same meaning as for sendmail(), except that msg is a Messageobject.

If from_addr is None or to_addrs is None, sendmessage fillsthose arguments with addresses extracted from the headers of _msg asspecified in RFC 5322: from_addr is set to the Sender_field if it is present, and otherwise to the _From field.to_addrs combines the values (if any) of the To,Cc, and Bcc fields from msg. If exactly oneset of Resent-* headers appear in the message, the regularheaders are ignored and the Resent-* headers are used instead.If the message contains more than one set of Resent-* headers,a ValueError is raised, since there is no way to unambiguously detectthe most recent set of Resent- headers.

sendmessage serializes _msg usingBytesGenerator with \r\n as the linesep, andcalls sendmail() to transmit the resulting message. Regardless of thevalues of from_addr and to_addrs, sendmessage does not transmit any_Bcc or Resent-Bcc headers that may appearin msg. If any of the addresses in from_addr and to_addrs containnon-ASCII characters and the server does not advertise SMTPUTF8 support,an SMTPNotSupported error is raised. Otherwise the Message isserialized with a clone of its policy with theutf8 attribute set to True, andSMTPUTF8 and BODY=8BITMIME are added to mail_options.

3.2 新版功能.

3.5 新版功能: Support for internationalized addresses (SMTPUTF8).

  • SMTP.quit()
  • Terminate the SMTP session and close the connection. Return the result ofthe SMTP QUIT command.

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 documentedhere. 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 headersto be included with the message must be included in the message as entered; thisexample 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.

  1. import smtplib
  2.  
  3. def prompt(prompt):
  4.     return input(prompt).strip()
  5.  
  6. fromaddr = prompt("From: ")
  7. toaddrs  = prompt("To: ").split()
  8. print("Enter message, end with ^D (Unix) or ^Z (Windows):")
  9.  
  10. # Add the From: and To: headers at the start!
  11. msg = ("From: %s\r\nTo: %s\r\n\r\n"
  12.        % (fromaddr, ", ".join(toaddrs)))
  13. while True:
  14.     try:
  15.         line = input()
  16.     except EOFError:
  17.         break
  18.     if not line:
  19.         break
  20.     msg = msg + line
  21.  
  22. print("Message length is", len(msg))
  23.  
  24. server = smtplib.SMTP('localhost')
  25. server.set_debuglevel(1)
  26. server.sendmail(fromaddr, toaddrs, msg)
  27. server.quit()

注解

In general, you will want to use the email package's features toconstruct an email message, which you can then sendvia send_message(); see email: 示例.