Set this up, allow no-auth sending from any address on your LAN, and then spinning up new local services that need outgoing mail is easy, because you can just give them the IP of the relay and omit credentials.
Reading through exim docs has taken hours of my life and it still caused weird issues. Using software that works for setting up a multinational email server to make your homelab send messages to Gmail is a massive time sink and kind of ridiculous really.
I haven't tested the code myself, but I'd prefer a simple system with limitations over a complex system that can be configured for simple tasks.
The nice thing about Apprise is that it can direct notifications to various places, not just another email server.
It is a need because it is a cancer that propagated to all big mail domain providers like gmail and microsoft 365. They are supposed to be business tools and still it is almost impossible to setup "device" email accounts that would identify just with credentials or equivalent without having to use a "web browser".