The Mail Editor module lets you edit the bodies and subjects of all emails that go out from your site to your users through Drupal's drupal_mail() function. You are able to edit any email body text based on which email it is and which language it is being sent for. You may use token variables in your templates to better customize dynamic email text.
Mail Editor has special support built-in for the User core module and the LoginToboggan module. Enable the Locale core module to activate non-English and even multi-lingual email template translation.
Mail Editor for Drupal 7
We recommend installing the Token module for assistance with editing the templates and to get access to the tokens that it provides.
Client modules can enhance Mail Editor by exposing additional standard token types and even adding types of their own. The Subscriptions module does this extensively, and it also adds a preview feature to Mail Editor.
Mail Editor's dynamic text goes far beyond simple token replacement: rich conditional and iterative constructs let your emails come alive, and Mail Editor enhances the Token module by providing numerical array indexing to enable looping over array tokens.
When combined with a module that provides an HTML-capable mail system, Mail Editor should in theory be capable of sending HTML mail. Let us know in the issues queue if you implement such a set-up.
Integration with the Features modules
Mail editor Features is a separate, independent module that provides the ability to import/export Mail Editor templates via the Features module.