FlexMailer (org.civicrm.flexmailer) is an email delivery engine for CiviCRM v4.7+. It replaces the internal guts of CiviMail. It is a drop-in replacement which enables other extensions to provide richer email features.

By default, FlexMailer supports the same user interfaces, delivery algorithms, and use-cases as CiviMail. After activating FlexMailer, an administrator does not need to take any special actions.

The distinguishing improvement here is under-the-hood: it provides better APIs and events for extension-developers. For example, other extensions might:

  • Change the template language
  • Manipulate tracking codes
  • Rework the delivery mechanism
  • Redefine the batching algorithm