EasyForms: MailFormDatabehavior ClassNotFoundException if parameter ef-use-freemarker is not set

Hippo version: 7.8.8
Hippo CMS version: 2.24.11
EasyForms version: 2.12.14
Tomcat 7.0.54

I followed the installarion steps on:
http://easy-forms.forge.onehippo.org/pluggable-behaviors/mailformdata.html

result: No e-mail was being sent
This error was being Logged:
WARNING] [talledLocalContainer] Jul 16, 2014 4:21:32 PM org.apache.catalina.core.StandardWrapperValve invoke
[WARNING] [talledLocalContainer] SEVERE: Servlet.service() for servlet [default] in context with path [/site] threw exception [Filter execution threw an exception] with root cause
[WARNING] [talledLocalContainer] java.lang.ClassNotFoundException: org.apache.velocity.app.VelocityEngine
[WARNING] [talledLocalContainer] at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1720)
[WARNING] [talledLocalContainer] at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1571)
[WARNING] [talledLocalContainer] at org.onehippo.forge.easyforms.util.VelocityParser.<init>(VelocityParser.java:196)
[WARNING] [talledLocalContainer] at org.onehippo.forge.easyforms.util.VelocityParser.<clinit>(VelocityParser.java:52)
[WARNING] [talledLocalContainer] at org.onehippo.forge.easyforms.behaviors.AbstractMailBehavior.getHtml(AbstractMailBehavior.java:144)

Workaround: set the parameter "ef-use-freemarker" to true