Newsletters: Filter Reference« Codex
The WordPress Newsletter plugin will fire filter hooks throughout it’s code so that you can hook with custom filters onto these filters hooks while receiving parameters and apply your own functions.
It works exactly like the WordPress Plugin API/Filter Reference by using the
apply_filters()function and the filter hooks are used in the same manner as that of WordPress.
This filter reference is constantly updated with new filter hooks as the plugin is updated so search here or request a new filter hook if you’re looking for something specific.
wpml_send_body– Filters the body/content of the email just before it is sent. Arguments: $body, $phpmailer, $history_id
wpml_extensions_list– Applied to the extensions list which is fetched. Arguments: $extensions