edit struts-config.xml

Add the following to the struts-config.xml in the 'form-beans' section.

<form-bean name="mailForm"
           type="org.apache.struts.action.DynaActionForm">
  <form-property name="subject" type="java.lang.String"/>
  <form-property name="sender" type="java.lang.String"/>
  <form-property name="recipients" type="java.lang.String"/>
  <form-property name="ccRecipients" type="java.lang.String"/>
  <form-property name="bccRecipients" type="java.lang.String"/>
  <form-property name="mailType" type="java.lang.String"/>
  <form-property name="url" type="java.lang.String"/>
  <form-property name="plainContent" type="java.lang.String"/>
  <form-property name="htmlContent" type="java.lang.String"/>
  <form-property name="attachments" type="java.lang.String"/>
 </form-bean>

and the following in the 'action-mappings' section

<action path="/sendform"
        input="/sendform.jsp"
        parameter="method"
        name="mailForm"
        type="neo.servlet.MailFormSender"
        validate="false"
        scope="request">
  <forward name="success" path="/success.jsp" redirect="true"/>
  <forward name="failure" path="/failure.jsp" redirect="true"/>
  </action>

Edit the paths to reflect your form.