Newsletters: Function Reference« Codex
The WordPress Newsletter plugin has it’s own custom functions similar to some of the WordPress query, template and internal functions which you can use during development.
New functions are constantly added to this documentation so please search or request a new function if you are looking for something specific.
Subscribe Form Functions
wpml_hardcode– Hardcode a subscribe form into any plugin or theme.
Mailing List Functions
wpml_get_mailinglists– Get an array of mailing list objects with the parameters of your choice.