In order for a user to receive an email, user must have both global subscription enabled, as well as the category-specific subscription enabled for the category in the context of which current mailing is executed. If a user opted-out from any of these two subscription types, no email is sent to the user.
Such two-level subscription model provides a more flexible approach for managing recipient opt-in. Users may select what kind of mailings they prefer to receive, and organizations may assign different subscription categories to different departments.
The end effect of global and category-based subscription is summarized in the following table:
User subscription management is provided by Arnica EmailServer via web service APIs, database APIs and program script APIs. Subscription may also be analyzed and updated using Arnica EmailServer Administrator module.