I'm new to KMail2 and akonadi.

Everything I've read indicates akonadi is a backend caching system to share PIM data. Everything I've read indicates that while akonadi cache files can be deleted, the actual data files are not touched except by the respecttive app.

When first using KMail2, I noticed emails being fetched by akonadi. If akonadi is a backend caching system then why is akonadi fetching mail instead of idling until the user explicitly starts KMail2?

I am aware of the KMail2 OfflineOnShutdown account setting, but having that setting is evidence that akonadi fetches mail without KMail2. Why is that setting needed?

I'm looking for an explanation. Nothing more.

Thanks.