Magento – Custom Magento transactional email template file location

Use the google url builder get a good campaign url: https://support.google.com/analytics/answer/1033867?hl=en

It will take your base url and create a tracking url based on your info that you add and presents a link like: http://www.savethemage.com/?utm_source=Newsletter&utm_medium=Email&utm_content=Logo&utm_campaign=Order+Confirmation

Then take the part starting with ?: ?utm_source=Newsletter&utm_medium=Email&utm_content=Logo&utm_campaign=Order+Confirmation

and add it to the transaction email template for each link you want to track. Make sure you change the utm_content= to something unique for each link.

Then analytics will track all of those clicks.

You would need to rewrite Mage_Core_Model_Email_Template_Mailer and you'll have to create a concrete method for the magic method setTemplateParams:

public function setTemplateParams($params)
{

    //you'll have to load your custom block and template - try it this way:
    $block = Mage::app()->getFrontController()->getLayout()->getBlock('custom/block');
    $block->setTemplate('custom/template.phtml');
    $html = $block->toHtml();

    $params['your_varname'] = $html;

    parent::setTemplateParams($params);

}

It's pretty simple - we're getting in between the magic method with a concrete method, injecting our template {{var your_varname}} handle for the email and then passing that up to the magic method!

Best of luck!