SMTP Objects¶

AnSMTP instance has the following methods:

SMTP.set_debuglevel(level)¶

Set the debug output level. A value of 1 orTrue forlevel results indebug messages for connection and for all messages sent to and received fromthe server. A value of 2 forlevel results in these messages beingtimestamped.

Changed in version 3.5:Added debuglevel 2.

SMTP.docmd(cmd,args='')¶

Send a commandcmd to the server. The optional argumentargs 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.

Raises anauditing eventsmtplib.connect with argumentsself,host,port.

SMTP.helo(name='')¶

Identify yourself to the SMTP server usingHELO. The hostname argumentdefaults to the fully qualified domain name of the local host.The message returned by the server is stored as thehelo_resp attributeof the object.

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

SMTP.ehlo(name='')¶

Identify yourself to an ESMTP server usingEHLO. The hostname argumentdefaults to the fully qualified domain name of the local host. Examine theresponse for ESMTP option and store them for use byhas_extn().Also sets several informational attributes: the message returned bythe server is stored as theehlo_resp attribute,does_esmtpis set toTrue orFalse depending on whether the server supportsESMTP, andesmtp_features will be a dictionary containing the namesof the SMTP service extensions this server supports, and their parameters(if any).

Unless you wish to usehas_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 callsehlo() and/orhelo() if there has been nopreviousEHLO orHELO command this session. It tries ESMTPEHLOfirst.

SMTPHeloError

The server didn’t reply properly to theHELO greeting.

SMTP.has_extn(name)¶

ReturnTrue ifname 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 SMTPVRFY. Returns atuple consisting of code 250 and a fullRFC 822 address (including humanname) if the user address is valid. Otherwise returns an SMTP error code of 400or greater and an error string.

Note

Many sites disable SMTPVRFY 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 orHELO command this session, this method tries ESMTPEHLOfirst. This method will return normally if the authentication was successful, ormay raise the following exceptions:

SMTPHeloError

The server didn’t reply properly to theHELO greeting.

SMTPAuthenticationError

The server didn’t accept the username/password combination.

SMTPNotSupportedError

TheAUTH command is not supported by the server.

SMTPException

No suitable authentication method was found.

Each of the authentication methods supported bysmtplib are tried inturn if they are advertised as supported by the server. Seeauth()for a list of supported authentication methods.initial_response_ok ispassed through toauth().

Optional keyword argumentinitial_response_ok specifies whether, forauthentication methods that support it, an “initial response” as specifiedinRFC 4954 can be sent along with theAUTH command, rather thanrequiring a challenge/response.

Changed in version 3.5:SMTPNotSupportedError may be raised, and theinitial_response_ok parameter was added.

SMTP.auth(mechanism,authobject,*,initial_response_ok=True)¶

Issue anSMTPAUTH command for the specified authenticationmechanism, and handle the challenge response viaauthobject.

mechanism specifies which authentication mechanism is tobe used as argument to theAUTH command; the valid values arethose listed in theauth element ofesmtp_features.

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

data=authobject(challenge=None)

If optional keyword argumentinitial_response_ok is true,authobject() will be called first with no argument. It can return theRFC 4954 “initial response” ASCIIstr which will be encoded and sent withtheAUTH command as below. If theauthobject() does not support aninitial response (e.g. because it requires a challenge), it should returnNone when called withchallenge=None. Ifinitial_response_ok isfalse, thenauthobject() will not be called first withNone.

If the initial response check returnsNone, or ifinitial_response_ok isfalse,authobject() will be called to process the server’s challengeresponse; thechallenge argument it is passed will be abytes. Itshould return ASCIIstrdata that will be base64 encoded and sent to theserver.

TheSMTP class providesauthobjects for theCRAM-MD5,PLAIN,andLOGIN mechanisms; they are namedSMTP.auth_cram_md5,SMTP.auth_plain, andSMTP.auth_login respectively. They all requirethat theuser andpassword properties of theSMTP instance areset to appropriate values.

User code does not normally need to callauth directly, but can insteadcall thelogin() 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 bysmtplib.

Added in version 3.5.

SMTP.starttls(*,context=None)¶

Put the SMTP connection in TLS (Transport Layer Security) mode. All SMTPcommands that follow will be encrypted. You should then callehlo()again.

Ifkeyfile andcertfile are provided, they are used to create anssl.SSLContext.

Optionalcontext parameter is anssl.SSLContext object; This isan alternative to using a keyfile and a certfile and if specified bothkeyfile andcertfile should beNone.

If there has been no previousEHLO orHELO command this session,this method tries ESMTPEHLO first.

Changed in version 3.12:The deprecatedkeyfile andcertfile parameters have been removed.

SMTPHeloError

The server didn’t reply properly to theHELO greeting.

SMTPNotSupportedError

The server does not support the STARTTLS extension.

RuntimeError

SSL/TLS support is not available to your Python interpreter.

Changed in version 3.3:context was added.

Changed in version 3.4:The method now supports hostname check withssl.SSLContext.check_hostname andServer Name Indicator (seeHAS_SNI).

Changed in version 3.5: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 anRFC 822 from-address string, a listofRFC 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 as8bitmime) to be used inMAILFROM commands asmail_options.ESMTP options (such asDSN commands) that should be used with allRCPTcommands can be passed asrcpt_options. (If you need to use different ESMTPoptions to different recipients you have to use the low-level methods such asmail(),rcpt() anddata() to send the message.)

Note

Thefrom_addr andto_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 previousEHLO orHELO command this session, thismethod tries ESMTPEHLO 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). IfEHLO 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.

IfSMTPUTF8 is included inmail_options, and the server supports it,from_addr andto_addrs may contain non-ASCII characters.

This method may raise the following exceptions:

SMTPRecipientsRefused

All recipients were refused. Nobody got the mail.

SMTPHeloError

The server didn’t reply properly to theHELO greeting.

SMTPSenderRefused

The server didn’t accept thefrom_addr.

SMTPDataError

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

SMTPNotSupportedError

SMTPUTF8 was given in themail_options but is not supported by theserver.

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

Changed in version 3.2:msg may be a byte string.

Changed in version 3.5:SMTPUTF8 support added, andSMTPNotSupportedError may beraised ifSMTPUTF8 is specified but the server does not support it.

SMTP.send_message(msg,from_addr=None,to_addrs=None,mail_options=(),rcpt_options=())¶

This is a convenience method for callingsendmail() with the messagerepresented by anemail.message.Message object. The arguments havethe same meaning as forsendmail(), except thatmsg is aMessageobject.

Iffrom_addr isNone orto_addrs isNone,send_message fillsthose arguments with addresses extracted from the headers ofmsg asspecified inRFC 5322:from_addr is set to theSenderfield if it is present, and otherwise to theFrom field.to_addrs combines the values (if any) of theTo,Cc, andBcc fields frommsg. If exactly oneset ofResent-* headers appear in the message, the regularheaders are ignored and theResent-* headers are used instead.If the message contains more than one set ofResent-* headers,aValueError is raised, since there is no way to unambiguously detectthe most recent set ofResent- headers.

send_message serializesmsg usingBytesGenerator with\r\n as thelinesep, andcallssendmail() to transmit the resulting message. Regardless of thevalues offrom_addr andto_addrs,send_message does not transmit anyBcc orResent-Bcc headers that may appearinmsg. If any of the addresses infrom_addr andto_addrs containnon-ASCII characters and the server does not advertiseSMTPUTF8 support,anSMTPNotSupportedError is raised. Otherwise theMessage isserialized with a clone of itspolicy with theutf8 attribute set toTrue, andSMTPUTF8 andBODY=8BITMIME are added tomail_options.

Added in version 3.2.

Added in version 3.5:Support for internationalized addresses (SMTPUTF8).

SMTP.quit()¶

Terminate the SMTP session and close the connection. Return the result ofthe SMTPQUIT command.

Low-level methods corresponding to the standard SMTP/ESMTP commandsHELP,RSET,NOOP,MAIL,RCPT, andDATA are also supported.Normally these do not need to be called directly, so they are not documentedhere. For details, consult the module code.

Additionally, an SMTP instance has the following attributes:

SMTP.helo_resp¶

The response to theHELO command, seehelo().

SMTP.ehlo_resp¶

The response to theEHLO command, seeehlo().

SMTP.does_esmtp¶

A boolean value indicating whether the server supports ESMTP, seeehlo().

SMTP.esmtp_features¶

A dictionary of the names of SMTP service extensions supported by the server,seeehlo().

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 theRFC 822 headers. In particular, the‘To’ and ‘From’ addresses must be included in the message headers explicitly:

importsmtplibdefprompt(title):returninput(title).strip()from_addr=prompt("From: ")to_addrs=prompt("To: ").split()print("Enter message, end with ^D (Unix) or ^Z (Windows):")# Add the From: and To: headers at the start!lines=[f"From:{from_addr}",f"To:{', '.join(to_addrs)}",""]whileTrue:try:line=input()exceptEOFError:breakelse:lines.append(line)msg="\r\n".join(lines)print("Message length is",len(msg))server=smtplib.SMTP("localhost")server.set_debuglevel(1)server.sendmail(from_addr,to_addrs,msg)server.quit()