It is important to have mass import users using CSV or EXCEL.
Totally agree, I have a site which has over 10000 users. Once I install the newsletter module I want to import those users into a newsletter list as well but I couldn't find a way.
The module should actually introduce a button labeled "Import existing users" and if clicked will do a batch process to import all existing users into a selected newsletter list.
Drupal is a registered trademark of Dries Buytaert.