This is really easily achievable on UNIX systems using the .forward (dot forward) file and your scripting language of choice. If you wanted to pipe all of root’s mail into a script, you would create a .forward file in that user’s home directory, consisting of a single line, starting with a pipe, followed by the full process path.

|/root/process.php

Then you need to provide a destination processor for your email. In this case we have used a UNIX-style file processor at the start by using the hashbang syntax:

#!/usr/local/bin/php
<?php

// read from stdin
$fp = fopen('php://stdin', 'r');
while(!feof($fp)) {
$lines[]=fgets($fp, 4096);
}

[... email processing code...]
?>

You can then use an optional MIME decoder such as Pear mimeDecode to break up the email into the relevant sections – for instance, the from/to fields and plain and/or HTML body text.