Feature Project Proposal: Notifications API

Most of the situations where WordPress sends an outgoing email can be classified as a notification. X just happened on your website and you should be aware of it. Back when WordPress was a youngster, the only way to reliably notify a user was via email. In 2016 we have many more options, including push notifications to mobile platforms, desktop notifications to browsers, messages to chat apps, endless services via webhooks, SMS messages, or even notifications in the WordPress admin area. The list goes on. For many users, email is no longer the optimal delivery mechanism for ephemeral notifications.
To that end, let’s think about replacing wp_mail() with a modern API that allows developers to route notifications to services other than email, allow them to better modify notifications and the way in which they’re formatted, and allow them to do so without stepping on each others’ toes.
The current lack of a notifications API (or even an email sending API) can be easily summed up:
Problem: Plugin A wants to provide HTML emails, and Plugin B wants to send emails via an email delivery service such as Mandrill. Plugin C wants to disregard emails and send Slack notifications.
Source: https://managewp.org/articles/13527/feature-project-proposal-notifications-api

source https://williechiu40.wordpress.com/2016/10/04/feature-project-proposal-notifications-api/