I’m not sure where I would put it but if you’re sending them directly from myapp_web maybe that would be the place but it does feel weird since it should be only responsible for the client-server interaction. But if you’re using an umbrella you could also have another app just responsible for that, on which myapp_web would depend. Then if you need to send notifications from myapp you can make it depend also on it.

Another thing to consider is if you use Oban or such to process the notifications sending, then that would live on myapp (or wherever you define your “workers”). I default to using Oban nowadays to process those kinds of things in a controlled fashion and so resort to placing the emailer dep. in whatever app defines the workers.