How do I implement a notification/subscription solution? I can't get the Notifications or Subscriptions modules to actually send out emails, and installing the Comment Notify module crashes my entire site.

I realize that Drupal 7 is still fairly young, but I find it pretty remarkable that there is not yet a stable notification/subscription solution. Does anyone have any suggestions beyond the modules I listed here?

Ideally, I would like the following features:


Automatically become subscribed to nodes you create or comment on (with the option to turn this off, of course)
Subscribe to taxonomy terms
Receive notification emails at an interval you specify, such as immediately, once a day, etc.


Seems like maybe 1 &amp; 2 are possible to do through Rules, which I'll begin to explore. But the third point above is pretty critical as well.
Have a look at the Message Stack, which consists of these modules (quotes are from the module's project page):

Message:

The Message module is the core of the message stack. It enables logging and displaying system events in a number of different use cases. Events that are recorded over time are sometimes call activity streams. Exportable messages subtypes can be created for different use cases with custom fields and display (view) modes.


Message Notify.

This module provides a method for sending a message via a notifier plugin. Message Notify comes with plugins for email and SMS and may be extended to other transport mechanisms as required.


Message Subscribe.

With this module, users who subscribe to content will be notified when events occur that involve that content. The module leverages the Flag module, which provides a subscribe functionality to users.



These are the basic components and dependencies of the message stack:

Quite a few popular Drupal distributions already adopted to this Message Stack, such as such as Commerce Kickstart, Drupal Commons, ERPAL and Open Atrium. And it will make you well positioned for Drupal 8 also (because of he modules' object orientated architecture).
If you want to have a closer look at the Message Stack in your own environment, then experiment a bit with the Answers module (disclosure: I'm a co-maintainer), together with the Answers Notification sub-module, which allows logged in users to subscribe to selected questions, so that they receive notifications (using the Message Stack) when Questions receive Answers.