imip-agent

Annotated docs/wiki/MailIntegration

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2016-02-08 Paul Boddie file changeset files shortlog Made the retraction operation a complete transaction. Tidied up the locking and unlocking function application.
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= Mail Integration =
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To act as a part of an e-mail system, imip-agent provides a number of programs
 
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that may be invoked by mail transfer agents (MTAs) upon sending or receiving
 
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messages. In order to uphold portability and to minimise configuration issues,
 
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these programs need only be registered as simple mail handlers or transports,
 
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thus potentially supporting a wide range of MTAs.
 
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Once imip-agent has processed a message, it may then deliver it to its
 
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intended recipient. The mail storage systems that may receive messages from
 
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imip-agent need only support the delivery mechanisms used by imip-agent.
 
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Otherwise, few constraints should be imposed by each kind of system on the
 
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other.
 
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{{{#!graphviz
 
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//format=svg
 
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//transform=notugly
 
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digraph mail_integration {
 
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  node [shape=box,fontsize="13.0",fontname="Helvetica",tooltip="Mail integration"];
 
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  edge [tooltip="Mail integration"];
 
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  rankdir=LR;
 
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  mail [label="Incoming mail",shape=folder,style=filled,fillcolor=cyan];
 
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  subgraph {
 
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    rank=same;
 
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    personrouter [label="Person router"];
 
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    resourcerouter [label="Resource router"];
 
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    recipients [label="Recipient database",shape=folder];
 
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  }
 
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  subgraph {
 
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    rank=same;
 
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    personhandler [label="Person handler",style=filled,fillcolor=gold];
 
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    resourcehandler [label="Resource handler",style=filled,fillcolor=gold];
 
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    scheduling [label="Scheduling",shape=ellipse,style=filled,fillcolor=gold];
 
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    freebusy [label="Free/busy",shape=folder,style=filled,fillcolor=gold];
 
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  }
 
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  mailbox [label="Mailboxes\n(Cyrus, Dovecot, ...)",tooltip="Mailboxes"];
 
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  mail -> personrouter -> personhandler -> mailbox;
 
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  mail -> resourcerouter -> resourcehandler
 
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  recipients -> personrouter;
 
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  recipients -> resourcerouter;
 
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  personhandler -> scheduling;
 
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  resourcehandler -> scheduling;
 
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  scheduling -> freebusy;
 
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}
 
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}}}
 
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== MTAs ==
 
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Currently, imip-agent supports [[http://exim.org/|Exim]] and
 
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[[http://www.postfix.org/|Postfix]], although this support should be readily
 
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broadened, and offers configuration resources for these supported systems so
 
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as to allow imip-agent to be deployed within existing mail-sending and
 
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delivery infrastructures.
 
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{{{#!table
 
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|| '''Identifying Recipients''' || '''Integrating imip-agent''' || '''Notes'''
 
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==
 
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'''Exim'''
 
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|| Routers identify recipients of mail that shall be handled by imip-agent
 
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|| Transports invoke imip-agent programs
 
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|| Exim is widely deployed as the default MTA for Debian. Consequently, it is
 
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.. desirable to support this software in imip-agent.
 
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==
 
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'''Postfix'''
 
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|| Virtual aliases identify recipients of mail that shall be handled by
 
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.. imip-agent
 
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|| Transports invoke imip-agent programs
 
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|| Postfix is also widely deployed and is sometimes preferred by administrators.
 
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}}}
 
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Some hints on mail system configuration can be found in the [[/MTA|MTA guide]].
 
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== Identification of Recipients ==
 
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In principle, any mechanism supported by the MTA can be used to identify
 
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recipients; imip-agent does not employ identification mechanisms of its own.
 
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Thus, the task of identifying recipients is one of MTA configuration, with the
 
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following mechanisms tested:
 
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{{{#!table
 
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'''Identification Mechanisms''' || '''Tested with...'''
 
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==
 
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[[/LDAP|LDAP]] || Exim, Postfix
 
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==
 
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[[/Simple|Simple (list-based identification)]] || Exim, Postfix
 
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}}}
 
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It is worth repeating that imip-agent does not try and validate users. Once
 
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the MTA has decided that a recipient can actually receive a message, and once
 
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that message is passed to one of the [[../AgentPrograms|agent programs]], the
 
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software will process that message and record information for the recipient in
 
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the [[../FilesystemUsage|filesystem structures]] for the user.
 
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See the [[../Usage|usage guide]] for information on preparing data stores for
 
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users in advance of any mail being received for them.
 
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=== The Calendar System Address ===
 
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Since imip-agent may send messages on behalf of calendar users, the address
 
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it uses to do so must be recognised by the MTA. This may be done by adding
 
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an entry to the `/etc/aliases` file such as the one defined in the
 
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`conf/aliases.example` file:
 
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{{{
 
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calendar: root
 
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}}}
 
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More suitable routing can be defined as desired. See the `MESSAGE_SENDER`
 
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setting defined in the `config.py` file described in the
 
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[[../Configuration|configuration guide]].
 
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== Invoking the Agent Programs ==
 
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Regardless of identification or delivery mechanisms, the imip-agent software
 
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must be integrated into the mail processing pipeline so that messages can be
 
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interpreted and processed. This is done by configuring the MTA's
 
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[[/Transports|transport mechanisms]].
 
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== Delivery ==
 
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To deliver messages to their ultimate recipients after having processed them,
 
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imip-agent currently employs either local SMTP connections or
 
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[[https://tools.ietf.org/html/rfc2033|LMTP]]. There is nothing in principle
 
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preventing imip-agent from also supporting other common delivery mechanisms,
 
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however.
 
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{{{#!table
 
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'''Delivery Mechanisms''' || '''Tested with...'''
 
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==
 
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[[/LocalSMTP|Local SMTP]] || Exim, Postfix
 
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==
 
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[[/LMTP|LMTP]]            || Exim, Postfix
 
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}}}
 
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See the [[../MailboxIntegration|mailbox integration guide]] for a brief
 
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overview of configuring mail storage solutions.