How to send mail from Liferay Portlet?

 import java.io.IOException;  
 import javax.mail.internet.AddressException;  
 import javax.mail.internet.InternetAddress;  
 import javax.portlet.ActionRequest;  
 import javax.portlet.ActionResponse;  
 import javax.portlet.PortletException;  
 import com.liferay.mail.service.MailServiceUtil;  
 import com.liferay.portal.kernel.mail.MailMessage;  
 import com.liferay.util.bridges.mvc.MVCPortlet;  
 /**  
  * Portlet implementation class FeedbackPortlet  
  */  
 public class FeedbackPortlet extends MVCPortlet {  
      public void sendEmail(ActionRequest actionRequest,  
                ActionResponse actionResponse) throws IOException, PortletException {  
           MailMessage mailMessage = new MailMessage();  
        mailMessage.setHTMLFormat(true);  
        mailMessage.setBody("Your mail body");  
        mailMessage.setFrom(new InternetAddress("from_mail_id@something.com","Display Name in Inbox"));  
        mailMessage.setSubject("Message From Feedback page...");  
        try {  
          mailMessage.setTo(new InternetAddress("to_mail_id@something.com"));  
        } catch (AddressException e) {  
          e.printStackTrace();  
        }  
        MailServiceUtil.sendEmail(mailMessage);   
        System.out.println("Sent Successfuly!!!");  
      }       
 }  

Before you go to run this portlet you have to make changes in Liferay configuration as below:

Step 1: Goto Liferay Control Panel
Step 2: In Configuration -> Click on Server Admninistration
Step 3: Then Goto Mail
Step 4: Fill out below fields(I am using GMail as my mail server),
a. Outgoing SMTP Server -> smtp.gmail.com
b. Outgoing Port  -> 465
c. Check -> Use a Secure Network Connection
d. User Name -> your_mail_id@gmail.com
e. Password -> your_gmail_password
Step 5: Click SAVE

Sometimes GMAIL can block the your application from sending mail as LESS SECURE application, in that case you again have to make change in gmail configuration as below:

Step 1: Goto Gmail Setting For Less Secure Applications
Step 2: Change setting for Access for less secure apps -> Turn on

Gmail Setting For Less Secure Applications

Thats it, now you will be able to send mail from your portlet.