pymodmilter

A pymilter based sendmail/postfix pre-queue filter with the ability to add, remove and modify e-mail headers.
The project is currently in beta status, but it is already used in a productive enterprise environment that processes about a million e-mails per month.

The basic idea is to define rules with conditions and actions which are processed when all conditions are true.

Dependencies

Pymodmilter is depending on these python packages, but they are installed automatically if you are working with pip.

• pymilter
• netaddr
• BeautifulSoup

Installation

• Install pymodmilter with pip and copy the example config file.

pip install pymodmilter
cp /etc/pymodmilter/pymodmilter.conf.example /etc/pymodmilter/pymodmilter.conf

• Modify /etc/pymodmilter/pymodmilter.conf according to your needs.

Configuration options

Pymodmilter uses a config file in JSON format. The config file has to be JSON valid with the exception of allowed comment lines starting with #. The options are described below.
Rules and actions are processed in the given order.

Global

Config options in global section:

• socket (optional)
  The socket used to communicate with the MTA. If it is not specified in the config, it has to be set as command line option.
• local_addrs (optional)
  A list of hosts and network addresses which are considered local. It is used to for the condition option local.
  Default: fe80::/64, ::1/128, 127.0.0.0/8, 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16
• loglevel (optional) Set the log level. This option may be overriden by any rule or action object. Possible values are:
  • error
  • warning
  • info
  • debug
    Default: info
• pretend (optional) Pretend actions, for test purposes. This option may be overriden by any rule or action object.

Rules

Config options for rule objects:

• name (optional)
  Name of the rule.
  Default: Rule #n
• actions
  A list of action objects which are processed in the given order.
• conditions (optional)
  A list of conditions which all have to be true to process the actions.
• loglevel (optional)
  As described above in the Global section.
• pretend (optional)
  As described above in the Global section.

Actions

Config options for action objects:

• name (optional)
  Name of the action. Default: Action #n
• type
  Action type. Possible values are:
  • add_header
  • del_header
  • mod_header
  • add_disclaimer
  • store
• conditions (optional)
  A list of conditions which all have to be true to process the action.
• loglevel (optional)
  As described above in the Global section.
• pretend (optional)
  As described above in the Global section.

Config options for add_header actions:

• field
  Name of the header.
• value
  Value of the header.

Config options for del_header actions:

• field
  Regular expression to match against header names.
• value (optional) Regular expression to match against the headers value.

Config options for mod_header actions:

• field
  Regular expression to match against header names.
• search (optional)
  Regular expression to match against header values. You may use subgroups or named subgroups (python syntax) to include parts of the original value in the new value.
• value
  New value of the header.

Config options for add_disclaimer actions:

• action
  Action to perform with the disclaimer. Possible values are:
  • append
  • prepend
• html_template
  Path to a file which contains the html representation of the disclaimer.
• text_template
  Path to a file which contains the text representation of the disclaimer.
• error_policy (optional)
  Set the error policy in case the disclaimer cannot be added (e.g. if no body part is present in the e-mail). Possible values are:
  • wrap
    A new e-mail body is generated with the disclaimer as body and the original e-mail attached.
  • ignore
    Ignore the error and do nothing.
  • reject
    Reject the e-mail. Default: wrap

Config options for store actions:

• storage_type
  Storage type. Possible values are:
  • file
• original (optional)
  Default: false If set to true, store the message as received by the MTA instead of storing the current state of the message, that may was modified already by other actions.

Config options for file storage:

• directory
  Directory used to store e-mails.

Conditions

Config options for conditions objects:

• local (optional)
  If set to true, the rule is only executed for e-mails originating from addresses defined in local_addrs and vice versa.
• hosts (optional)
  A list of hosts and network addresses for which the rule should be executed.
• envfrom (optional)
  A regular expression to match against the evenlope-from addresses for which the rule should be executed.
• envto (optional)
  A regular expression to match against all evenlope-to addresses. All addresses must match to fulfill the condition.

Developer information

Everyone who wants to improve or extend this project is very welcome.