C dkim milter for postfix

I need a standalone C milter that will help in signing mails with dkim signatures The most important requirement is performance The milter needs to sign only .. no need for checking signatures. This is a very heavy traffic mail server with 300k to 500k mails per hour on a 8GB RAM Dual Quadcore running Linux Centos 5.5 For the dkim There will be a config file that will define the milter behaviour The config file will contain parameters like pidfile , socketfile , headers to be used for the signature The configfile will also contain multiple key-records Each key-record will consist of 1) dkim private key 2) selector 3) domains to be used in dkim 4) email id to add for abuse header All these domains will be called as dkim-domains The config file should be read at the time of startup. The milter should not require the config file again When a mail arrives the dkim signature should be added on the selected domain which is listed in the config file The selected domain is chosen by extracting domain from email ids like this if headerfrom domain is a dkim domain use this else if envelope-from domain is a dkim domain use this else if X-Abuse-To is a dkim domain use this else add a nodkim header and skip this mail After signing the mail all the memory allocated should be freed up. After the project is complete this needs to be checked for memory leaks using valgrind.