How to send category based order emails in magento?

Question

I have two root categories in my magento site. One is \"Home Products\" and the other is \"Office products\".

These two root categories have some sub categories also.

Answer 1

@Jevgeni (and anyone else needing the link), the Link for Magento has moved

http://www.magentocommerce.com/wiki/5_-_modules_and_development/0_-_module_development_in_magento/customizing_magento_using_event-observer_method