[TYPO3-mvc] Where is the right place for methods like sendEmailAfterNewObjectIsSaved() in your extbase extension?

[Roland]

>> should it be instantiated via dependency injection?
>
>
> That doesn't really matter. But yes :)

could it be that you can not create an object based on a class located 
in the service folder via DI? i successfully inject a repository in this 
controller, but i fail injecting my service. creating the object via 
t3lib_div::makeInstance works. wired. where is MY fault? wired.

roland