20.16. smtpd
— SMTP Server¶
Source code: Lib/smtpd.py
This module offers several classes to implement SMTP (email) servers.
Several server implementations are present; one is a generic do-nothing implementation, which can be overridden, while the other two offer specific mail-sending strategies.
Additionally the SMTPChannel may be extended to implement very specific interaction behaviour with SMTP clients.
20.16.1. SMTPServer Objects¶
-
class
smtpd.
SMTPServer
(localaddr, remoteaddr)¶ Create a new
SMTPServer
object, which binds to local address localaddr. It will treat remoteaddr as an upstream SMTP relayer. It inherits fromasyncore.dispatcher
, and so will insert itself intoasyncore
‘s event loop on instantiation.-
process_message
(peer, mailfrom, rcpttos, data)¶ Raise
NotImplementedError
exception. Override this in subclasses to do something useful with this message. Whatever was passed in the constructor as remoteaddr will be available as the_remoteaddr
attribute. peer is the remote host’s address, mailfrom is the envelope originator, rcpttos are the envelope recipients and data is a string containing the contents of the e-mail (which should be in RFC 2822 format).
-
channel_class
¶ Override this in subclasses to use a custom
SMTPChannel
for managing SMTP clients.
-
20.16.2. DebuggingServer Objects¶
-
class
smtpd.
DebuggingServer
(localaddr, remoteaddr)¶ Create a new debugging server. Arguments are as per
SMTPServer
. Messages will be discarded, and printed on stdout.
20.16.3. PureProxy Objects¶
-
class
smtpd.
PureProxy
(localaddr, remoteaddr)¶ Create a new pure proxy server. Arguments are as per
SMTPServer
. Everything will be relayed to remoteaddr. Note that running this has a good chance to make you into an open relay, so please be careful.
20.16.4. MailmanProxy Objects¶
-
class
smtpd.
MailmanProxy
(localaddr, remoteaddr)¶ Create a new pure proxy server. Arguments are as per
SMTPServer
. Everything will be relayed to remoteaddr, unless local mailman configurations knows about an address, in which case it will be handled via mailman. Note that running this has a good chance to make you into an open relay, so please be careful.
20.16.5. SMTPChannel Objects¶
-
class
smtpd.
SMTPChannel
(server, conn, addr)¶ Create a new
SMTPChannel
object which manages the communication between the server and a single SMTP client.To use a custom SMTPChannel implementation you need to override the
SMTPServer.channel_class
of yourSMTPServer
.The
SMTPChannel
has the following instance variables:-
smtp_server
¶ Holds the
SMTPServer
that spawned this channel.
-
conn
¶ Holds the socket object connecting to the client.
-
addr
¶ Holds the address of the client, the second value returned by socket.accept()
-
received_lines
¶ Holds a list of the line strings (decoded using UTF-8) received from the client. The lines have their “rn” line ending translated to “n”.
-
smtp_state
¶ Holds the current state of the channel. This will be either
COMMAND
initially and thenDATA
after the client sends a “DATA” line.
-
seen_greeting
¶ Holds a string containing the greeting sent by the client in its “HELO”.
-
mailfrom
¶ Holds a string containing the address identified in the “MAIL FROM:” line from the client.
-
rcpttos
¶ Holds a list of strings containing the addresses identified in the “RCPT TO:” lines from the client.
-
received_data
¶ Holds a string containing all of the data sent by the client during the DATA state, up to but not including the terminating “rn.rn”.
-
fqdn
¶ Holds the fully-qualified domain name of the server as returned by
socket.getfqdn()
.
The
SMTPChannel
operates by invoking methods namedsmtp_<command>
upon reception of a command line from the client. Built into the baseSMTPChannel
class are methods for handling the following commands (and responding to them appropriately):Command Action taken HELO Accepts the greeting from the client and stores it in seen_greeting
.NOOP Takes no action. QUIT Closes the connection cleanly. MAIL Accepts the “MAIL FROM:” syntax and stores the supplied address as mailfrom
.RCPT Accepts the “RCPT TO:” syntax and stores the supplied addresses in the rcpttos
list.RSET Resets the mailfrom
,rcpttos
, andreceived_data
, but not the greeting.DATA Sets the internal state to DATA
and stores remaining lines from the client inreceived_data
until the terminator “rn.rn” is received.-