= INSTALLATION =

To install this module, run the following commands:

    perl Makefile.PL
    make
    make install

= CONFIGURE =

Add 'Filter::CheckMessageId' to the list of mail plugins in RT_SiteConfig.pm.

Restart web server.

If you are running RT-3.8 you will need to use slightly different syntax

Set(@MailPlugins, qw(CheckMessageId));

= PERFORMANCE ISSUE =

This plugin search messages Id in column 'messageid' of the table 'attachments'.
It is strongly recommanded to create an index to speed-up the search in this
table.

Connect to the database:

CREATE INDEX messageid_idx ON attachments (messageid);

Enjoy.