Searching a performant Newsletter Modul

[Tobel]

Hello

We have build a web application on a Tomcat Servlet Container. Now we
want to send newsletters to registered customers. The range ist between
1000 and 10000 letters, so it would be nice, if it can be launched
apart on an extra machine to reduce server load. Therefore we are
searching for some existing Framework oder Modul, we can integrate.
Does anyone know a performant one?


Thanks for help,

Tobel