21.18. smtpd — SMTP 服务器 ¶

创建新的 SMTPServer object, which binds to local address localaddr . It will treat remoteaddr as an upstream SMTP relayer. Both localaddr and remoteaddr should be a (host, port) tuple. The object inherits from asyncore.dispatcher , and so will insert itself into asyncore ’s event loop on instantiation.

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.

map is the socket map to use for connections (an initially empty dictionary is a suitable value). If not specified the asyncore global socket map is used.

enable_SMTPUTF8 determines whether the SMTPUTF8 extension (as defined in RFC 6531 ) should be enabled. The default is False 。当 True , SMTPUTF8 is accepted as a parameter to the MAIL command and when present is passed to process_message() 在 kwargs['mail_options'] list. decode_data and enable_SMTPUTF8 cannot be set to True at the same time.

decode_data specifies whether the data portion of the SMTP transaction should be decoded using UTF-8. When decode_data is False (the default), the server advertises the 8BITMIME extension ( RFC 6152 ), accepts the BODY=8BITMIME parameter to the MAIL command, and when present passes it to process_message() 在 kwargs['mail_options'] list. decode_data and enable_SMTPUTF8 cannot be set to True at the same time.

process_message ( peer , mailfrom , rcpttos , data , **kwargs ) ¶

引发 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 属性。 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 5321 format).

若 decode_data constructor keyword is set to True ， data argument will be a unicode string. If it is set to False , it will be a bytes object.

kwargs is a dictionary containing additional information. It is empty if decode_data=True was given as an init argument, otherwise it contains the following keys:

mail_options :

a list of all received parameters to the MAIL command (the elements are uppercase strings; example: ['BODY=8BITMIME', 'SMTPUTF8'] ).

rcpt_options :

如同 mail_options but for the RCPT command. Currently no RCPT TO options are supported, so for now this will always be an empty list.

实现的 process_message should use the **kwargs signature to accept arbitrary keyword arguments, since future feature enhancements may add keys to the kwargs dictionary.

返回 None to request a normal 250 Ok response; otherwise return the desired response string in RFC 5321 格式。

channel_class ¶

Override this in subclasses to use a custom SMTPChannel for managing SMTP clients.

Create a new debugging server. Arguments are as per SMTPServer . Messages will be discarded, and printed on stdout.

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.

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.

创建新的 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 determines whether the SMTPUTF8 extension (as defined in RFC 6531 ) should be enabled. The default is False . decode_data and enable_SMTPUTF8 cannot be 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 False . decode_data and enable_SMTPUTF8 cannot be set to True at the same time.

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

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 .

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):