Magento – Magento – How to restrict coupon codes to specific email id

If you've already generated the codes and associated them with a rule, you can look the code up by the rule id. We recently did something similar but had the codes auto generated based on rule id - I found this extension helpful:

http://www.magentocommerce.com/magento-connect/newsletter-subscription-with-free-gift-coupon.html

It may not be exactly what you're looking for, but you could modify it to suit your needs.

$appliedRuleIds = Mage::getSingleton('checkout/session')->getQuote()->getAppliedRuleIds();

This will give you the ids of the rules applied to the quote separated by comma.
you can turn them into an array like this:

$appliedRuleIds = explode(',', $appliedRuleIds);

if you want to get the rules applied as objects you can do this:

//$rules = Mage::getModel('salesrule/rule')->getCollection()->addFieldToFilter('rule_id' => array('in' => $appliedRuleIds));
$rules =  Mage::getModel('salesrule/rule')->getCollection()->addFieldToFilter('rule_id' , array('in' => $appliedRuleIds));

foreach ($rules as $rule) {
    //do something with $rule
}