smtplib.py

#! /usr/bin/env python

'''SMTP/ESMTP client class.

This should follow RFC 821 (SMTP), RFC 1869 (ESMTP), RFC 2554 (SMTP
Authentication) and RFC 2487 (Secure SMTP over TLS).

Notes:

Please remember, when doing ESMTP, that the names of the SMTP service
extensions are NOT the same thing as the option keywords for the RCPT
and MAIL commands!

Example:

  >>> import smtplib
  >>> s=smtplib.SMTP("localhost")
  >>> print s.help()
  This is Sendmail version 8.8.4
  Topics:
      HELO    EHLO    MAIL    RCPT    DATA
      RSET    NOOP    QUIT    HELP    VRFY
      EXPN    VERB    ETRN    DSN
  For more info use "HELP <topic>".
  To report bugs in the implementation send email to
      sendmail-bugs@sendmail.org.
  For local information send email to Postmaster at your site.
  End of HELP info
  >>> s.putcmd("vrfy","someone@here")
  >>> s.getreply()
  (250, "Somebody OverHere <somebody@here.my.org>")
  >>> s.quit()
'''

# Author: The Dragon De Monsyne <dragondm@integral.org>
# ESMTP support, test code and doc fixes added by
#     Eric S. Raymond <esr@thyrsus.com>
# Better RFC 821 compliance (MAIL and RCPT, and CRLF in data)
#     by Carey Evans <c.evans@clear.net.nz>, for picky mail servers.
# RFC 2554 (authentication) support by Gerhard Haering <gerhard@bigfoot.de>.
#
# This was modified from the Python 1.5 library HTTP lib.

import socket
import re
import email.utils
import base64
import hmac
from email.base64mime import encode as encode_base64
from sys import stderr

from tornado import gen
from tornado import iostream

__all__ = ["SMTPException","SMTPServerDisconnected","SMTPResponseException",
           "SMTPSenderRefused","SMTPRecipientsRefused","SMTPDataError",
           "SMTPConnectError","SMTPHeloError","SMTPAuthenticationError",
           "quoteaddr","quotedata","SMTP"]

SMTP_PORT = 25
SMTP_SSL_PORT = 465
CRLF = "\r\n"

OLDSTYLE_AUTH = re.compile(r"auth=(.*)", re.I)


# Exception classes used by this module.
class SMTPException(Exception):
    """Base class for all exceptions raised by this module."""

class SMTPServerDisconnected(SMTPException):
    """Not connected to any SMTP server.

    This exception is raised when the server unexpectedly disconnects,
    or when an attempt is made to use the SMTP instance before
    connecting it to a server.
    """

class SMTPResponseException(SMTPException):
    """Base class for all exceptions that include an SMTP error code.

    These exceptions are generated in some instances when the SMTP
    server returns an error code.  The error code is stored in the
    `smtp_code' attribute of the error, and the `smtp_error' attribute
    is set to the error message.
    """

    def __init__(self, code, msg):
        self.smtp_code = code
        self.smtp_error = msg
        self.args = (code, msg)

class SMTPSenderRefused(SMTPResponseException):
    """Sender address refused.

    In addition to the attributes set by on all SMTPResponseException
    exceptions, this sets `sender' to the string that the SMTP refused.
    """

    def __init__(self, code, msg, sender):
        self.smtp_code = code
        self.smtp_error = msg
        self.sender = sender
        self.args = (code, msg, sender)

class SMTPRecipientsRefused(SMTPException):
    """All recipient addresses refused.

    The errors for each recipient are accessible through the attribute
    'recipients', which is a dictionary of exactly the same sort as
    SMTP.sendmail() returns.
    """

    def __init__(self, recipients):
        self.recipients = recipients
        self.args = (recipients,)


class SMTPDataError(SMTPResponseException):
    """The SMTP server didn't accept the data."""

class SMTPConnectError(SMTPResponseException):
    """Error during connection establishment."""

class SMTPHeloError(SMTPResponseException):
    """The server refused our HELO reply."""

class SMTPAuthenticationError(SMTPResponseException):
    """Authentication error.

    Most probably the server didn't accept the username/password
    combination provided.
    """


def quoteaddr(addr):
    """Quote a subset of the email addresses defined by RFC 821.

    Should be able to handle anything rfc822.parseaddr can handle.
    """
    m = (None, None)
    try:
        m = email.utils.parseaddr(addr)[1]
    except AttributeError:
        pass
    if m == (None, None):  # Indicates parse failure or AttributeError
        # something weird here.. punt -ddm
        return "<%s>" % addr
    elif m is None:
        # the sender wants an empty return address
        return "<>"
    else:
        return "<%s>" % m

def quotedata(data):
    """Quote data for email.

    Double leading '.', and change Unix newline '\\n', or Mac '\\r' into
    Internet CRLF end-of-line.
    """
    return re.sub(r'(?m)^\.', '..',
        re.sub(r'(?:\r\n|\n|\r(?!\n))', CRLF, data))


try:
    import ssl
except ImportError:
    _have_ssl = False
else:
    class SSLFakeFile:
        """A fake file like object that really wraps a SSLObject.

        It only supports what is needed in smtplib.
        """
        def __init__(self, sslobj):
            self.sslobj = sslobj

        def readline(self):
            str = ""
            chr = None
            while chr != "\n":
                chr = self.sslobj.read(1)
                if not chr:
                    break
                str += chr
            return str

        def close(self):
            pass

    _have_ssl = True

class SMTP:
    """This class manages a connection to an SMTP or ESMTP server.
    SMTP Objects:
        SMTP objects have the following attributes:
            helo_resp
                This is the message given by the server in response to the
                most recent HELO command.

            ehlo_resp
                This is the message given by the server in response to the
                most recent EHLO command. This is usually multiline.

            does_esmtp
                This is a True value _after you do an EHLO command_, if the
                server supports ESMTP.

            esmtp_features
                This is a dictionary, which, if the server supports ESMTP,
                will _after you do an EHLO command_, contain the names of the
                SMTP service extensions this server supports, and their
                parameters (if any).

                Note, all extension names are mapped to lower case in the
                dictionary.

        See each method's docstrings for details.  In general, there is a
        method of the same name to perform each SMTP command.  There is also a
        method called 'sendmail' that will do an entire mail transaction.
        """
    debuglevel = 0
    file = None
    helo_resp = None
    ehlo_msg = "ehlo"
    ehlo_resp = None
    does_esmtp = 0
    default_port = SMTP_PORT

    def __init__(self, host='', port=0, local_hostname=None,
                 timeout=socket._GLOBAL_DEFAULT_TIMEOUT):
        """Initialize a new instance.

        If specified, `host' is the name of the remote host to which to
        connect.  If specified, `port' specifies the port to which to connect.
        By default, smtplib.SMTP_PORT is used.  An SMTPConnectError is raised
        if the specified `host' doesn't respond correctly.  If specified,
        `local_hostname` is used as the FQDN of the local host.  By default,
        the local hostname is found using socket.getfqdn().

        """
        self.timeout = timeout
        self.esmtp_features = {}
        if host:
            (code, msg) = self.connect(host, port)
            if code != 220:
                raise SMTPConnectError(code, msg)
        if local_hostname is not None:
            self.local_hostname = local_hostname
        else:
            # RFC 2821 says we should use the fqdn in the EHLO/HELO verb, and
            # if that can't be calculated, that we should use a domain literal
            # instead (essentially an encoded IP address like [A.B.C.D]).
            fqdn = socket.getfqdn()
            if '.' in fqdn:
                self.local_hostname = fqdn
            else:
                # We can't find an fqdn hostname, so use a domain literal
                addr = '127.0.0.1'
                try:
                    addr = socket.gethostbyname(socket.gethostname())
                except socket.gaierror:
                    pass
                self.local_hostname = '[%s]' % addr

    def set_debuglevel(self, debuglevel):
        """Set the debug output level.

        A non-false value results in debug messages for connection and for all
        messages sent to and received from the server.

        """
        self.debuglevel = debuglevel

    @gen.engine
    def _get_stream(self, host, port, timeout, callback):
        sock, sockaddr = self._get_socket(host, port, timeout)
        stream = iostream.IOStream(sock)
        yield gen.Task(stream.connect, sockaddr)
        callback(stream)

    @gen.engine
    def _get_ssl_stream(self, host, port, timeout, callback):
        sock, sockaddr = self._get_ssl_socket(host, port, timeout)
        stream = iostream.SSLIOStream(sock)
        yield gen.Task(stream.connect, sockaddr)
        callback(stream)

    def _get_socket(self, host, port, timeout):
        # This makes it simpler for SMTP_SSL to use the SMTP connect code
        # and just alter the socket connection bit.
        if self.debuglevel > 0: print>>stderr, 'connect:', (host, port)
        sock = sockaddr = None
        for res in socket.getaddrinfo(host, port, 0, socket.SOCK_STREAM):
            family, socktype, proto, canonname, sockaddr = res
            try:
                sock = socket.socket(family, socktype, proto)
                break
            except socket.error:
                sock = None
        if not sock:
            raise
        if timeout is not socket._GLOBAL_DEFAULT_TIMEOUT:
            sock.settimeout(timeout)
        return sock, sockaddr

    def _get_ssl_socket(self, stream, do_handshake_on_connect=False, **kwds):
        sock, sockaddr = self._get_socket(host, port, timeout)
        kwds['do_handshake_on_connect'] = False
        sock = ssl.wrap_socket(sock, **kwds)
        return sock, sockaddr

    @gen.engine
    def connect(self, host='localhost', port=0, callback=None):
        """Connect to a host on a given port.

        If the hostname ends with a colon (`:') followed by a number, and
        there is no port specified, that suffix will be stripped off and the
        number interpreted as the port number to use.

        Note: This method is automatically invoked by __init__, if a host is
        specified during instantiation.

        """
        if not port and (host.find(':') == host.rfind(':')):
            i = host.rfind(':')
            if i >= 0:
                host, port = host[:i], host[i + 1:]
                try:
                    port = int(port)
                except ValueError:
                    raise socket.error, "nonnumeric port"
        if not port:
            port = self.default_port
        if self.debuglevel > 0:
            print>>stderr, 'connect:', (host, port)
        self.sock = yield gen.Task(self._get_stream, host, port, self.timeout)
        (code, msg) = yield gen.Task(self.getreply)
        if self.debuglevel > 0:
            print>>stderr, "connect:", msg
        if callback:
            callback((code, msg))

    def send(self, str, callback):
        """Send `str' to the server."""
        if self.debuglevel > 0:
            print>>stderr, 'send:', repr(str)
        if hasattr(self, 'sock') and self.sock:
            try:
                self.sock.write(str, callback)
            except socket.error:
                self.close()
                raise SMTPServerDisconnected('Server not connected')
        else:
            raise SMTPServerDisconnected('please run connect() first')

    def putcmd(self, cmd, args="", callback=None):
        """Send a command to the server."""
        if args == "":
            str = '%s%s' % (cmd, CRLF)
        else:
            str = '%s %s%s' % (cmd, args, CRLF)
        self.send(str, callback)

    @gen.engine
    def getreply(self, callback):
        """Get a reply from the server.

        Returns a tuple consisting of:

          - server response code (e.g. '250', or such, if all goes well)
            Note: returns -1 if it can't read response code.

          - server response string corresponding to response code (multiline
            responses are converted to a single, multiline string).

        Raises SMTPServerDisconnected if end-of-file is reached.
        """
        resp = []
        while 1:
            try:
                line = yield gen.Task(self.sock.read_until, '\n')
            except socket.error:
                line = ''
            if line == '':
                self.close()
                raise SMTPServerDisconnected("Connection unexpectedly closed")
            if self.debuglevel > 0:
                print>>stderr, 'reply:', repr(line)
            resp.append(line[4:].strip())
            code = line[:3]
            # Check that the error code is syntactically correct.
            # Don't attempt to read a continuation line if it is broken.
            try:
                errcode = int(code)
            except ValueError:
                errcode = -1
                break
            # Check if multiline response.
            if line[3:4] != "-":
                break

        errmsg = "\n".join(resp)
        if self.debuglevel > 0:
            print>>stderr, 'reply: retcode (%s); Msg: %s' % (errcode, errmsg)
        callback((errcode, errmsg))

    @gen.engine
    def docmd(self, cmd, args="", callback=None):
        """Send a command, and return its response code."""
        yield gen.Task(self.putcmd, cmd, args)
        self.getreply(callback)

    # std smtp commands
    @gen.engine
    def helo(self, name='', callback=None):
        """SMTP 'helo' command.
        Hostname to send for this command defaults to the FQDN of the local
        host.
        """
        yield gen.Task(self.putcmd, "helo", name or self.local_hostname)
        (code, msg) = yield gen.Task(self.getreply)
        self.helo_resp = msg
        if callback:
            callback((code, msg))

    @gen.engine
    def ehlo(self, name='', callback=None):
        """ SMTP 'ehlo' command.
        Hostname to send for this command defaults to the FQDN of the local
        host.
        """
        self.esmtp_features = {}
        yield gen.Task(self.putcmd, self.ehlo_msg, name or self.local_hostname)
        (code, msg) = yield gen.Task(self.getreply)
        # According to RFC1869 some (badly written)
        # MTA's will disconnect on an ehlo. Toss an exception if
        # that happens -ddm
        if code == -1 and len(msg) == 0:
            self.close()
            raise SMTPServerDisconnected("Server not connected")
        self.ehlo_resp = msg
        if code != 250:
            if callback:
                callback((code, msg))
            return
        self.does_esmtp = 1
        #parse the ehlo response -ddm
        resp = self.ehlo_resp.split('\n')
        del resp[0]
        for each in resp:
            # To be able to communicate with as many SMTP servers as possible,
            # we have to take the old-style auth advertisement into account,
            # because:
            # 1) Else our SMTP feature parser gets confused.
            # 2) There are some servers that only advertise the auth methods we
            #    support using the old style.
            auth_match = OLDSTYLE_AUTH.match(each)
            if auth_match:
                # This doesn't remove duplicates, but that's no problem
                self.esmtp_features["auth"] = self.esmtp_features.get("auth", "") \
                        + " " + auth_match.groups(0)[0]
                continue

            # RFC 1869 requires a space between ehlo keyword and parameters.
            # It's actually stricter, in that only spaces are allowed between
            # parameters, but were not going to check for that here.  Note
            # that the space isn't present if there are no parameters.
            m = re.match(r'(?P<feature>[A-Za-z0-9][A-Za-z0-9\-]*) ?', each)
            if m:
                feature = m.group("feature").lower()
                params = m.string[m.end("feature"):].strip()
                if feature == "auth":
                    self.esmtp_features[feature] = self.esmtp_features.get(feature, "") \
                            + " " + params
                else:
                    self.esmtp_features[feature] = params
        if callback:
            callback((code, msg))

    def has_extn(self, opt):
        """Does the server support a given SMTP service extension?"""
        return opt.lower() in self.esmtp_features

    @gen.engine
    def help(self, args='', callback=None):
        """SMTP 'help' command.
        Returns help text from server."""
        yield gen.Task(self.putcmd, "help", args)
        (code, msg) = yield gen.Task(self.getreply)
        if callback:
            callback(msg)

    def rset(self, callback):
        """SMTP 'rset' command -- resets session."""
        self.docmd("rset", callback=callback)

    def noop(self, callback):
        """SMTP 'noop' command -- doesn't do anything :>"""
        self.docmd("noop", callback=callback)

    @gen.engine
    def mail(self, sender, options=[], callback=None):
        """SMTP 'mail' command -- begins mail xfer session."""
        optionlist = ''
        if options and self.does_esmtp:
            optionlist = ' ' + ' '.join(options)
        yield gen.Task(self.putcmd, "mail", "FROM:%s%s" % (quoteaddr(sender), optionlist))
        self.getreply(callback)

    @gen.engine
    def rcpt(self,recip,options=[], callback=None):
        """SMTP 'rcpt' command -- indicates 1 recipient for this mail."""
        optionlist = ''
        if options and self.does_esmtp:
            optionlist = ' ' + ' '.join(options)
        yield gen.Task(self.putcmd, "rcpt", "TO:%s%s" % (quoteaddr(recip), optionlist))
        self.getreply(callback)

    @gen.engine
    def data(self, msg, callback=None):
        """SMTP 'DATA' command -- sends message data to server.

        Automatically quotes lines beginning with a period per rfc821.
        Raises SMTPDataError if there is an unexpected reply to the
        DATA command; the return value from this method is the final
        response code received when the all data is sent.
        """
        yield gen.Task(self.putcmd, "data")
        (code, repl) = yield gen.Task(self.getreply)
        if self.debuglevel > 0:
            print>>stderr, "data:", (code, repl)
        if code != 354:
            raise SMTPDataError(code, repl)
        else:
            q = quotedata(msg)
            if q[-2:] != CRLF:
                q = q + CRLF
            q = q + "." + CRLF
            yield gen.Task(self.send, q)
            (code, msg) = yield gen.Task(self.getreply)
            if self.debuglevel > 0:
                print>>stderr, "data:", (code, msg)
            if callback:
                callback((code, msg))

    @gen.engine
    def verify(self, address, callback):
        """SMTP 'verify' command -- checks for address validity."""
        yield gen.Task(self.putcmd, "vrfy", quoteaddr(address))
        self.getreply(callback)
    # a.k.a.
    vrfy = verify

    @gen.engine
    def expn(self, address, callback):
        """SMTP 'expn' command -- expands a mailing list."""
        yield gen.Task(self.putcmd, "expn", quoteaddr(address))
        self.getreply(callback)

    # some useful methods

    @gen.engine
    def ehlo_or_helo_if_needed(self, callback):
        """Call self.ehlo() and/or self.helo() if needed.

        If there has been no previous EHLO or HELO command this session, this
        method tries ESMTP EHLO first.

        This method may raise the following exceptions:

         SMTPHeloError            The server didn't reply properly to
                                  the helo greeting.
        """
        if self.helo_resp is None and self.ehlo_resp is None:
            (code, resp) = yield gen.Task(self.ehlo)
            if not (200 <= code <= 299):
                (code, resp) = yield gen.Task(self.helo)
                if not (200 <= code <= 299):
                    raise SMTPHeloError(code, resp)
        callback()


    @gen.engine
    def login(self, user, password, callback=None):
        """Log in on an SMTP server that requires authentication.

        The arguments are:
            - user:     The user name to authenticate with.
            - password: The password for the authentication.

        If there has been no previous EHLO or HELO command this session, this
        method tries ESMTP EHLO first.

        This method will return normally if the authentication was successful.

        This method may raise the following exceptions:

         SMTPHeloError            The server didn't reply properly to
                                  the helo greeting.
         SMTPAuthenticationError  The server didn't accept the username/
                                  password combination.
         SMTPException            No suitable authentication method was
                                  found.
        """

        def encode_cram_md5(challenge, user, password):
            challenge = base64.decodestring(challenge)
            response = user + " " + hmac.HMAC(password, challenge).hexdigest()
            return encode_base64(response, eol="")

        def encode_plain(user, password):
            return encode_base64("\0%s\0%s" % (user, password), eol="")


        AUTH_PLAIN = "PLAIN"
        AUTH_CRAM_MD5 = "CRAM-MD5"
        AUTH_LOGIN = "LOGIN"

        yield gen.Task(self.ehlo_or_helo_if_needed)

        if not self.has_extn("auth"):
            raise SMTPException("SMTP AUTH extension not supported by server.")

        # Authentication methods the server supports:
        authlist = self.esmtp_features["auth"].split()

        # List of authentication methods we support: from preferred to
        # less preferred methods. Except for the purpose of testing the weaker
        # ones, we prefer stronger methods like CRAM-MD5:
        preferred_auths = [AUTH_CRAM_MD5, AUTH_PLAIN, AUTH_LOGIN]

        # Determine the authentication method we'll use
        authmethod = None
        for method in preferred_auths:
            if method in authlist:
                authmethod = method
                break

        if authmethod == AUTH_CRAM_MD5:
            (code, resp) = yield gen.Task(self.docmd, "AUTH", AUTH_CRAM_MD5)
            if code == 503:
                # 503 == 'Error: already authenticated'
                if callback:
                    callback((code, resp))
                return
            (code, resp) = yield gen.Task(self.docmd, encode_cram_md5(resp, user, password))
        elif authmethod == AUTH_PLAIN:
            (code, resp) = yield gen.Task(self.docmd, "AUTH",
                AUTH_PLAIN + " " + encode_plain(user, password))
        elif authmethod == AUTH_LOGIN:
            (code, resp) = yield gen.Task(self.docmd, "AUTH",
                "%s %s" % (AUTH_LOGIN, encode_base64(user, eol="")))
            if code != 334:
                raise SMTPAuthenticationError(code, resp)
            (code, resp) = yield gen.Task(self.docmd, encode_base64(password, eol=""))
        elif authmethod is None:
            raise SMTPException("No suitable authentication method found.")
        if code not in (235, 503):
            # 235 == 'Authentication successful'
            # 503 == 'Error: already authenticated'
            raise SMTPAuthenticationError(code, resp)
        if callback:
            callback((code, resp))

    @gen.engine
    def starttls(self, keyfile=None, certfile=None, callback=None):
        """Puts the connection to the SMTP server into TLS mode.

        If there has been no previous EHLO or HELO command this session, this
        method tries ESMTP EHLO first.

        If the server supports TLS, this will encrypt the rest of the SMTP
        session. If you provide the keyfile and certfile parameters,
        the identity of the SMTP server and client can be checked. This,
        however, depends on whether the socket module really checks the
        certificates.

        This method may raise the following exceptions:

         SMTPHeloError            The server didn't reply properly to
                                  the helo greeting.
        """
        yield gen.Task(self.ehlo_or_helo_if_needed)
        if not self.has_extn("starttls"):
            raise SMTPException("STARTTLS extension not supported by server.")
        (resp, reply) = yield gen.Task(self.docmd, "STARTTLS")
        if resp == 220:
            if not _have_ssl:
                raise RuntimeError("No SSL support included in this Python")
            #FIXME!
            self.sock = yield gen.Task(
                self._get_ssl_socket, self.sock,
                keyfile=keyfile, certfile=certfile
            )
            # RFC 3207:
            # The client MUST discard any knowledge obtained from
            # the server, such as the list of SMTP service extensions,
            # which was not obtained from the TLS negotiation itself.
            self.helo_resp = None
            self.ehlo_resp = None
            self.esmtp_features = {}
            self.does_esmtp = 0
        if callback:
            callback((resp, reply))

    @gen.engine
    def sendmail(self, from_addr, to_addrs, msg, mail_options=[],
                 rcpt_options=[], callback=None):
        """This command performs an entire mail transaction.

        The arguments are:
            - from_addr    : The address sending this mail.
            - to_addrs     : A list of addresses to send this mail to.  A bare
                             string will be treated as a list with 1 address.
            - msg          : The message to send.
            - mail_options : List of ESMTP options (such as 8bitmime) for the
                             mail command.
            - rcpt_options : List of ESMTP options (such as DSN commands) for
                             all the rcpt commands.

        If there has been no previous EHLO or HELO command this session, this
        method tries ESMTP EHLO first.  If the server does ESMTP, message size
        and each of the specified options will be passed to it.  If EHLO
        fails, HELO will be tried and ESMTP options suppressed.

        This method will return normally if the mail is accepted for at least
        one recipient.  It returns a dictionary, with one entry for each
        recipient that was refused.  Each entry contains a tuple of the SMTP
        error code and the accompanying error message sent by the server.

        This method may raise the following exceptions:

         SMTPHeloError          The server didn't reply properly to
                                the helo greeting.
         SMTPRecipientsRefused  The server rejected ALL recipients
                                (no mail was sent).
         SMTPSenderRefused      The server didn't accept the from_addr.
         SMTPDataError          The server replied with an unexpected
                                error code (other than a refusal of
                                a recipient).

        Note: the connection will be open even after an exception is raised.

        Example:

         >>> import smtplib
         >>> s=smtplib.SMTP("localhost")
         >>> tolist=["one@one.org","two@two.org","three@three.org","four@four.org"]
         >>> msg = '''\\
         ... From: Me@my.org
         ... Subject: testin'...
         ...
         ... This is a test '''
         >>> s.sendmail("me@my.org",tolist,msg)
         { "three@three.org" : ( 550 ,"User unknown" ) }
         >>> s.quit()

        In the above example, the message was accepted for delivery to three
        of the four addresses, and one was rejected, with the error code
        550.  If all addresses are accepted, then the method will return an
        empty dictionary.

        """
        yield gen.Task(self.ehlo_or_helo_if_needed)
        esmtp_opts = []
        if self.does_esmtp:
            # Hmmm? what's this? -ddm
            # self.esmtp_features['7bit']=""
            if self.has_extn('size'):
                esmtp_opts.append("size=%d" % len(msg))
            for option in mail_options:
                esmtp_opts.append(option)

        (code, resp) = yield gen.Task(self.mail, from_addr, esmtp_opts)
        if code != 250:
            yield gen.Task(self.rset)
            raise SMTPSenderRefused(code, resp, from_addr)
        senderrs = {}
        if isinstance(to_addrs, basestring):
            to_addrs = [to_addrs]
        for each in to_addrs:
            (code, resp) = yield gen.Task(self.rcpt, each, rcpt_options)
            if (code != 250) and (code != 251):
                senderrs[each] = (code, resp)
        if len(senderrs) == len(to_addrs):
            # the server refused all our recipients
            yield gen.Task(self.rset)
            raise SMTPRecipientsRefused(senderrs)
        (code, resp) = yield gen.Task(self.data, msg)
        if code != 250:
            yield gen.Task(self.rset)
            raise SMTPDataError(code, resp)
        #if we got here then somebody got our mail
        if callback:
            callback(senderrs)


    def close(self):
        """Close the connection to the SMTP server."""
        if self.sock:
            self.sock.close()
        self.sock = None

    @gen.engine
    def quit(self, callback=None):
        """Terminate the SMTP session."""
        res = yield gen.Task(self.docmd, "quit")
        self.close()
        if callback:
            callback(res)