I have a common scenario that I am looking for some guidance from people more experienced with DDD and Domain Modeling in general.
Say I start out building a blog engine
Have you considered having the article controller essentially pass a message up / post an event? Then any "article-posted-event-listeners" would consume that message and respond accordingly; in your specific case, an email notifier would be listening for those events and be configured to do so. This way the article posting bits don't need to know anything about the email notifying bits.