I think I agree with sv3tli0 that this would have to be an add-on. Although I do agree that email queues are very important. But as already mentioned so are queues for image processing, or file uploading.
Any queue for CI would have to be a generalized queue not built specifically for email. It would have to have a queue name (for different queues), and some way for timing the queues, and some generalized way of triggering different events, since not every host has access to cron jobs like some shared hosting platforms. In fact I have no idea how all that could actually work.
So although I like the idea of a generalized queue, or a specific email queue, I think that like the shopping cart class or user management, it is not something that can be easily generalized to suit everyone or anyone, and most people needing such functionality would use either a more specific third party app or build their own.
Just my thoughts,
Best wishes,
Paul.
