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+#title Sender Address Verifier for Sendmail
+#style /web/default.css
+
+
+Author: Wolfgang Hottgenroth <woho@hottis.de>, 2004-05-17
+
+
+
+
+This is the prototype of a sender address verifier for sendmail-8.13.
+
+It consists of a m4 file containing a FEATURE to be included in your
+=sendmail.mc= and a verifier daemon in a bit of python code.
+
+
+By including the FEATURE in your sendmail.mc file and running the
+verifier daemon, sendmail file verify either
+
+- all sender addresses (with certain exceptions) or
+- only certain sender addresses
+
+This will be done by connecting to the best MX servers of the
+particular domain, trying to send a mail to the particular address and
+collect the replies. 
+
+Actually only the =HELO=, =MAIL= and =RCPT= commands are issued.
+
+If a positive reply was found, the mail is considered as valid.
+
+If a permanent negative reply was found, the mail is considered as
+invalid.
+
+If no MX entry was found, the mail is considered as invalid.
+
+If a temporary negative reply was found, the mail is considered as
+temporary invalid.
+
+If there is more than one best MX server all of these servers are
+connected in parallel and the first permanent reply (either positive
+or negative) is returned.
+
+
+** Download
+
+The complete sources: [[./download/][download]]
+
+Have a look into the sources: [[http://www.hottis.de/cgi-bin/cvsweb.cgi/sender_verifier/][sources]]
+
+
+
+
+** Requirements
+
+*** sendmail
+
+sendmail-8.13 is required, since this thing uses the fresh introduced
+socket map.
+
+Find it [[http://www.sendmail.org][here]] on the sendmail homepage.
+
+Your need to build sendmail with support for the socket map. Include 
+
+<example>
+APPENDDEF(`confMAPDEF',`-DSOCKETMAP')
+</example>
+
+in your =site.config.m4=.
+
+
+*** Python
+
+Python 2.2 or 2.3 is required. If you have Python 2.3 you must delete
+the =import timeoutsocket= line from =verifier.py=.
+
+Additionally the python package =python-dns= is required. Find it
+[[http://pydns.sourceforge.net/][http://pydns.sourceforge.net]].
+
+
+
+** Configuration of sendmail
+
+Include the FEATURE in your =sendmail.mc= file. You need to give two
+parameters:
+
+<example>
+FEATURE(`verifysender', `mode', `return')
+</example>
+
+For =mode= you must give either =white= or =black=.
+
+=white= :: All sender addresses but those mentioned in the whitelist
+file are verified. Complete addresses or just domains can be listed in
+the file. The default location of the whitelist is
+=/etc/mail/verify-white-list=. If you need a different location,
+define it to =confVERIFIER_WHITELIST=.
+
+=black= :: only addresses or addresses within domains listed in the
+blacklist file are verified. It is obviously only useful to mention
+domains in the blacklist. The default location of the blacklist is
+=/etc/mail/verify-black-list=. If you need a different location,
+define it to =confVERIFIER_BLACKLIST=.
+
+Both the blacklist and the whitelist file are maps, they must be
+created with =makemap=. Therefore the entries need a LHS (the address
+or domain) and a RHS. The actual content of the RHS has NO meaning at
+all.
+
+The FEATURE defines a socket map. The default target of the map is
+=inet:8884@127.0.0.1=, according to the default setting in
+=Config.py=. If you need something different, define it to
+=confVERIFIER_MAP=, but don't forget to also adjust =Config.py=.
+
+
+** Configuration of the verification daemon
+
+The configuration of the daemon is done in the file =Config.py=.
+
+This is the default of this file:
+
+<example>
+[Daemon]
+Address: 127.0.0.1
+Port: 8884
+PidFile: smmapd.pid
+Plugins: Verifier,Verifier2
+
+[Logging]
+ApplId: smmapd
+
+[Verifier]
+ContainerModule: VerifierHandler
+ContainerClass: VerifierHandlerContainer
+WorkerModule: VerifierHandler
+WorkerClass: VerifierHandlerWorker
+EnableCaching: 1
+CacheExpiration: 20
+SMTPTimeOut: 20
+SMTPHeloParam: local
+SMTPCheckSender: <>
+
+[Verifier2]
+ContainerModule: VerifierHandler
+ContainerClass: VerifierHandlerContainer
+WorkerModule: VerifierHandler
+WorkerClass: VerifierHandlerWorker
+EnableCaching: 1
+CacheExpiration: 20
+SMTPTimeOut: 20
+SMTPHeloParam: hottis.de
+SMTPCheckSender: <postmaster@hottis.de></example>
+
+=Port= and =Address= are specifying the socket the daemon should
+listen to for communication with sendmail. These settings must be
+reflected in the =confVERIFIER_MAP= if you change it.
+
+=SMTPTimeOut= is the timeout for the communication with the MX servers
+when verifying addresses.
+
+=SMTPHeloParam= is the parameter the verifier will use with the =HELO=
+command when verifying.
+
+=SMTPCheckSender= is the sender address used during
+verifications. You should not change it unless you know what you do to
+avoid verification loops.
+
+Since the verification is a time and resource consuming process,
+results can be cached, which is enabled by default. Set
+=EnableCaching= to 0 to disable it.
+
+=CacheExpiration= is the time in seconds an entry in the cache is
+considered as valid. It should be much higher.
+
+
+** Operation
+
+Configure sendmail and the daemon according to your needs. Start the
+daemon:
+
+<example>
+./verifier.py
+</example>
+
+
+** Changes
+
+- According to a comment in comp.mail.sendmail I've introduced a class
+  =verifier_fix_white= in the FEATURE file, currently containing only
+  the string =postmaster=. Addresses with userpart in this class will
+  never ever be verified to avoid infinite verifying loops.
+
+*** 2004-05-17
+- support plugins
+- separate container and worker object, thereby enable multiple
+  instances of the same plugins
+