smtpd.SMTPChannel

class smtpd.SMTPChannel(server, conn, addr, data_size_limit=33554432, map=None, enable_SMTPUTF8=False, decode_data=True)

Create a new SMTPChannel object which manages the communication between the server and a single SMTP client.

conn and addr are as per the instance variables described below.

data_size_limit specifies the maximum number of bytes that will be accepted in a DATA command. A value of None or 0 means no limit.

enable_SMTPUTF8 determins whether the SMTPUTF8 extension (as defined in RFC 6531) should be enabled. The default is False. A ValueError is raised if both enable_SMTPUTF8 and decode_data are set to True at the same time.

A dictionary can be specified in map to avoid using a global socket map.

decode_data specifies whether the data portion of the SMTP transaction should be decoded using UTF-8. The default is True for backward compatibility reasons, but will change to False in Python 3.6. Specify the keyword value explicitly to avoid the DeprecationWarning.

To use a custom SMTPChannel implementation you need to override the SMTPServer.channel_class of your SMTPServer.

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 "\r\n" line ending translated to "\n".

smtp_state

Holds the current state of the channel. This will be either COMMAND initially and then DATA 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 "\r\n.\r\n".

fqdn

Holds the fully-qualified domain name of the server as returned by socket.getfqdn().

peer

Holds the name of the client peer as returned by conn.getpeername() where conn is conn.

The SMTPChannel operates by invoking methods named smtp_<command> upon reception of a command line from the client. Built into the base SMTPChannel 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. Sets server to base command mode.
EHLO	Accepts the greeting from the client and stores it in seen_greeting. Sets server to extended command mode.
NOOP	Takes no action.
QUIT	Closes the connection cleanly.
MAIL	Accepts the “MAIL FROM:” syntax and stores the supplied address as mailfrom. In extended command mode, accepts the RFC 1870 SIZE attribute and responds appropriately based on the value of data_size_limit.
RCPT	Accepts the “RCPT TO:” syntax and stores the supplied addresses in the rcpttos list.
RSET	Resets the mailfrom, rcpttos, and received_data, but not the greeting.
DATA	Sets the internal state to DATA and stores remaining lines from the client in received_data until the terminator "\r\n.\r\n" is received.
HELP	Returns minimal information on command syntax
VRFY	Returns code 252 (the server doesn’t know if the address is valid)
EXPN	Reports that the command is not implemented.