Tomcat is a complete web server written in Java that provides support for the Servlet and JSP specifications. Tomcat is developed as a part of the Apache Jakarta Project. Both binaries and source are available from the Jakarta web site.

To run the JakartaMailServlet, you must add the Jakarta Mail and JavaBeans Activation Framework jar files to the `lib` directory under the directory in which you installed Tomcat. This will cause Tomcat to include these jar files in its classpath automatically. (Some packages of Tomcat version 4 include Jakarta Mail support.) Depending on the version of Tomcat used, the `mail.jar` and `activation.jar` files should be copied to the `lib` directory or to an appropriate subdirectory of the `lib` directory.