Erro em sevlet após envio da mesma pro servidor

Nao tem mais nada nos logs?

javax.servlet.ServletException: Cannot allocate servlet instance for path /servlet/Email at org.apache.catalina.servlets.InvokerServlet.serveRequest(InvokerServlet.java:415) at org.apache.catalina.servlets.InvokerServlet.doPost(InvokerServlet.java:216) at javax.servlet.http.HttpServlet.service(HttpServlet.java:760) at javax.servlet.http.HttpServlet.service(HttpServlet.java:853) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:247) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:243) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:190) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566) at org.apache.catalina.valves.CertificatesValve.invoke(CertificatesValve.java:246) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943) at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2343) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566) at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:170) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:170) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943) at org.apache.ajp.tomcat4.Ajp13Processor.process(Ajp13Processor.java:429) at org.apache.ajp.tomcat4.Ajp13Processor.run(Ajp13Processor.java:495) at java.lang.Thread.run(Thread.java:536)

root cause

java.lang.NoClassDefFoundError: javax/mail/MessagingException at java.lang.Class.getDeclaredConstructors0(Native Method) at java.lang.Class.privateGetDeclaredConstructors(Class.java:1590) at java.lang.Class.getConstructor0(Class.java:1762) at java.lang.Class.newInstance0(Class.java:276) at java.lang.Class.newInstance(Class.java:259) at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:884) at org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:653) at org.apache.catalina.servlets.InvokerServlet.serveRequest(InvokerServlet.java:396) at org.apache.catalina.servlets.InvokerServlet.doPost(InvokerServlet.java:216) at javax.servlet.http.HttpServlet.service(HttpServlet.java:760) at javax.servlet.http.HttpServlet.service(HttpServlet.java:853) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:247) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:243) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:190) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566) at org.apache.catalina.valves.CertificatesValve.invoke(CertificatesValve.java:246) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943) at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2343) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566) at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:170) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:170) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943) at org.apache.ajp.tomcat4.Ajp13Processor.process(Ajp13Processor.java:429) at org.apache.ajp.tomcat4.Ajp13Processor.run(Ajp13Processor.java:495) at java.lang.Thread.run(Thread.java:536)

package email;
import java.io.IOException;
import java.io.PrintWriter;

import javax.mail.MessagingException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Email extends HttpServlet {

	/**
	 * The doPost method of the servlet. <br>
	 *
	 * This method is called when a form has its tag value method equals to post.
	 * @param request the request send by the client to the server
	 * @param response the response send by the server to the client
	 * @throws ServletException if an error occurred
	 * @throws IOException if an error occurred
	 */
	public void doPost(
		HttpServletRequest request,
		HttpServletResponse response)
		throws ServletException, IOException {

		response.setContentType("text/html");
		PrintWriter out = response.getWriter();
		
		String nome = request.getParameter("nome");
		String mensagem = request.getParameter("mensagem");
		String email = request.getParameter("email");
		String para = "[email removido]";
		String assunto = request.getParameter("assunto");
		
		try {
			String message = nome + "<br>" + mensagem;
			EmailBean.postMail(message,para,email,assunto);
			out.println("<h2>Mensagem enviada com sucesso</h2>");
		} catch (MessagingException e) {
			out.println(e.getMessage()+"<br>Falha ao enviar o email<br>");
			out.println(e.getStackTrace()+"<br>é a lista completa de erros");		
		}
			
	}

}

<servlet>
    <servlet-name>Email</servlet-name>
    <servlet-class>email.Email</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>Email</servlet-name>
    <url-pattern>/servlet/Email</url-pattern>
  </servlet-mapping>

coloca os jars do javamail no WEB-INF/lib da tua aplicação