Alternatives to Messaging and Notifications I maintain a Drupal 6 site for a team of scuba-divers.
Given the discontinued support for Drupal 6, I am looking at upgrading the site to Drupal 7.

We primarily communicate by e-mail, so we have set up a Messaging+Notifications thing, where users can subscribe to new nodes of a given node-type, with one primary purpose: When a boat-commander arranges a new diving trip (node-type) all interested divers receive a notification mail, so they can sign-in to the trip.
The same functionality goes for clubhouse events and articles in general (secondary).

Mails are formatted so, that they contain a link to the node on the site (obviously), and they also contain a link to unsubscribe to further mails of same kind.

It seems Messaging+Notifications are not (actively) maintained on D7, so I am looking for an alternative.

I have tried a Commons distro, but I just cannot get the grasp of the Messages (log?) and Flags concept. It seems to me that it is build to click-to-follow existing posts, but I want to have the option to always follow posts of a certain kind.

Am I misunderstanding the Messages module, or am I looking at a wrong module?
A project that is similar in scope to Notifications and is actively supported for Drupal 7 is Subscriptions.

You may also want to look at some of the more lightweight notification modules. The project Notify is designed to send out notifications whenever new content of a certain content type appear (Disclosure: I am the maintainer of Notify).

There is a Notifications via e-mail comparison at Groups.Drupal.org. This gives you a good idea of what is available for Drupal 7.