Nodemailer v2.1.0-rc.0 is the first rc release for the v2.1.0 version. Stable is released 7 days after the last rc version, so for now the stable is planned for january 27th.
Install it with:
npm install nodemailer@beta
Notable changes are related to better custom headers support and templating. Templating can be used with built-in simple rendering or by providing a node-email-templates renderer, see the docs for examples.
The relase of v2.1.0-rc.1 moved stable release date to february 1st.