[tomwalsham]

This strikes me as somewhat of an edge case - to add a full rules engine for what is essentially a very app-specific set of behaviours.

One main reason the application is the best place to manage these rules is that it's rarely just the email content that dictates the engagement pipeline. Whether a user has interacted with a component, or logged in, etc, are all app-side variables which may affect whether or not you wish to send a given email.

That said, one method some of our customers use at PostageApp to simplify some of the logic is to pass a UID to the API based on the unique parameter sets - e.g. recipient + template + hour - and rely on the engine to discard the duplicate API calls.

[aidos]

I guess my concern is that you end up coupling components with marketing rules where there would otherwise be little or no connection.