java.lang.ClassNotFoundException: javax.mail.MessagingException

Please help me to resolve this issue

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.Properties;

import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.Session;
import javax.mail.Transport;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class ForgotPassword
 */
public class ForgotPassword extends HttpServlet {
	private static final long serialVersionUID = 1L;
    PrintWriter out=null;   
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    	try 
    	{
    		response.setContentType("text/html");
    		out=response.getWriter();
    		Class.forName("oracle.jdbc.driver.OracleDriver");
    		Connection connection = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521","system","password");
    		Statement st = connection.createStatement();
    		ResultSet rs = st.executeQuery("select * from dbusers");
    		String nickname = request.getParameter("nickname");
    		String username = request.getParameter("username");
    		String uname=null;
    		String pwd=null;
    		String uname2=null;
    		while(rs.next()) 
    		{
    			if (nickname.equals(rs.getString("nickname")) || username.equals(rs.getString("username"))) 
    			{
    				uname = rs.getString("username");
    				pwd = rs.getString("password1");
    				uname2 = "found"; 
    			}
    			else 
    			{
    				uname2 = "not found";
    			}
    		}
    		if(uname2=="not found")
    		{
    			out.println("<html>");
    			out.println("<head>");
    			out.println("<style type='text/css'>p{font-family:Arial Black, Gadget, sans-serif};}</style>");
    			out.println("<body bgcolor='lightblue'>");
    			out.println("<br><h2><center><p class='sans-serif'>");
    			out.println("<br>You are not a registered user</p>");
    			out.println("<br><br>");
    			out.println("<a href='invalidLogin.jsp'><h2><i>SIGNUP HERE</i></h2></a>");
    			out.println("</center></h2></body></html>");
    		}
    		if(uname2=="found")
    		{
    		  // Recipient's email ID 
  		      String to = rs.getString("email");

// Sender's email ID 
  		      String from = "grksharma9@yahoo.com";

// Host name
  		      String host = "mail.somecompanyname.com";

// Get system properties
  		      Properties properties = System.getProperties();

// Setup mail server
  		      properties.setProperty("mail.smtp.host", host);

// Get the default Session object.
  		      Session session = Session.getDefaultInstance(properties);

try{
  		         // Creating a default MimeMessage object.
  		         MimeMessage message = new MimeMessage(session);

// From: header field of the header.
  		         message.setFrom(new InternetAddress(from));

// To: header field of the header.
  		         message.addRecipient(Message.RecipientType.TO, new InternetAddress(to));

// Subject: header field
  		         message.setSubject("Username and Password");

//  actual message
  		         message.setText("Username is: "+uname);
  		         message.setText("Password is: "+pwd);

// Send message
  		         Transport.send(message);
  		         }
  		      catch (MessagingException mex) {
  		         mex.printStackTrace();
  		      }
    		}
    	}
       	catch (Exception e) 
       	{
       		System.out.println(e);
       	}
    }
}

And i got the exception says
java.lang.ClassNotFoundException: javax.mail.MessagingException
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1680)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1526)
at java.lang.ClassLoader.loadClassInternal(Unknown Source)
at java.lang.Class.getDeclaredConstructors0(Native Method)
at java.lang.Class.privateGetDeclaredConstructors(Unknown Source)
at java.lang.Class.getConstructor0(Unknown Source)
at java.lang.Class.newInstance0(Unknown Source)
at java.lang.Class.newInstance(Unknown Source)
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1116)
at org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:809)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:129)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Unknown Source)

The JavaMail JAR file mail.jar is not on your class path.

Thank you spoor,
I just added that jar file to build path.
But when i copied it to tomcat lib folder, it worked.