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 which processes about a million e-mails per month.

The basic idea is to define rules with conditions and do modifications when all conditions are met.

Requirements

• pymilter https://pythonhosted.org/pymilter/
• netaddr https://github.com/drkjam/netaddr/

Configuration

Pymodmilter uses a configuration file in JSON format. The options are described below. Make a copy of the example configuration file in the docs folder to start with.

global (Object)

The following optional global configuration options are available:

• local_addrs (Array of Strings)
  A list of hosts and network addresses which are considered local. It is used to for the condition option 'local'. This option may be overriden within a rule object.
• log (Bool)
  Enable or disable logging. This option may be overriden by a rule or modification object.

rules (Array)

A mandatory list of rule objects which are processed in the given order.

rule (Object)

The following configuration options are mandatory for each rule:

• modifications (Array of Objects)
  A list of modification objects which are processed in the given order.

The following configuration options are optional for each rule:

• name (String)
  Name of the rule.
• conditions (Object)
  A list of conditions which all have to be true to process the rule.
• local_addrs (Array of Strings)
  As described above in the global object section.
• log (Bool)
  As described above in the global object section.

modification (Object)

The following configuration options are mandatory for each modification:

• type (String)
  Set the modification type. Possible values are:
  • add_header
  • del_header
  • mod_header

Additional parameters are mandatory based on the modification type.

• add_header

  • header (String)
    Name of the header.
  • value (String)
    Value of the header.

• del_header

  • header (String)
    Regular expression to match against header lines.

• mod_header

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

The following configuration options are optional for each modification:

• name (String)
  Name of the modification.
• log (Bool)
  As described above in the global object section.

conditions (Object)

The following configuration options are optional:

• local (Bool)
  If set to true, the rule is only executed for emails originating from addresses defined in local_addrs and vice versa.
• hosts (Array of Strings)
  A list of hosts and network addresses for which the rule should be executed.
• envfrom (String)
  A regular expression to match against the evenlope-from addresses for which the rule should be executed.

Developer information

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