Send Emails in Background in Android.without user interaction...

Step-1
First of all Download 3 Jar files from http://code.google.com/p/javamail-android/downloads/list. (Ref. "http://stackoverflow.com/questions/2020088/sending-email-in-android-using-javamail-api-without-using-the-default-android-a")
activation.jar
additional.jar
mail.jar

Step-2
copy and paste those jar files into your project. then
Integrate all above jar files into your project
Right click on your project --> Properties -->
Java Build path --> Libraries --> Add JARs--> Add all 3 jars

Now go to Next Tab "Order and Export"--> select all --> Ok

Step-3
Create one class

import java.util.Date;
import java.util.Properties;

import javax.activation.CommandMap;
import javax.activation.DataHandler;
import javax.activation.DataSource;
import javax.activation.FileDataSource;
import javax.activation.MailcapCommandMap;
import javax.mail.BodyPart;
import javax.mail.Multipart;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMultipart;

public class GMailSender extends javax.mail.Authenticator {
    private String _user;
      private String _pass;
   
      private String[] _to;
      private String _from;
   
      private String _port;
      private String _sport;
   
      private String _host;
   
      private String _subject;
      private String _body;
   
      private boolean _auth;
      
      private boolean _debuggable;
   
      private Multipart _multipart;
   
   
      public GMailSender() {
        _host = "smtp.gmail.com"; // default smtp server
        _port = "465"; // default smtp port
        _sport = "465"; // default socketfactory port
   
        _user = ""; // username
        _pass = ""; // password
        _from = ""; // email sent from
        _subject = ""; // email subject
        _body = ""; // email body
   
        _debuggable = false; // debug mode on or off - default off
        _auth = true; // smtp authentication - default on
   
        _multipart = new MimeMultipart();
   
        // There is something wrong with MailCap, javamail can not find a handler for the multipart/mixed part, so this bit needs to be added.
        MailcapCommandMap mc = (MailcapCommandMap) CommandMap.getDefaultCommandMap();
        mc.addMailcap("text/html;; x-java-content-handler=com.sun.mail.handlers.text_html");
        mc.addMailcap("text/xml;; x-java-content-handler=com.sun.mail.handlers.text_xml");
        mc.addMailcap("text/plain;; x-java-content-handler=com.sun.mail.handlers.text_plain");
        mc.addMailcap("multipart/*;; x-java-content-handler=com.sun.mail.handlers.multipart_mixed");
        mc.addMailcap("message/rfc822;; x-java-content-handler=com.sun.mail.handlers.message_rfc822");
        CommandMap.setDefaultCommandMap(mc);
      }
   
      public GMailSender(String user, String pass) {
        this();
   
        _user = user;
        _pass = pass;
      }
   
      public boolean send() throws Exception {
        Properties props = _setProperties();
   
        if(!_user.equals("") && !_pass.equals("") && _to.length > 0 && !_from.equals("") && !_subject.equals("") && !_body.equals("")) {
          Session session = Session.getInstance(props, this);
   
          MimeMessage msg = new MimeMessage(session);
   
          msg.setFrom(new InternetAddress(_from));
          
          InternetAddress[] addressTo = new InternetAddress[_to.length];
          for (int i = 0; i < _to.length; i++) {
            addressTo[i] = new InternetAddress(_to[i]);
          }
            msg.setRecipients(MimeMessage.RecipientType.TO, addressTo);
   
          msg.setSubject(_subject);
          msg.setSentDate(new Date());
   
          // setup message body
          BodyPart messageBodyPart = new MimeBodyPart();
          messageBodyPart.setText(_body);
          _multipart.addBodyPart(messageBodyPart);
   
          // Put parts in message
          msg.setContent(_multipart);
   
          // send email
          Transport.send(msg);
   
          return true;
        } else {
          return false;
        }
      }
   
      public void addAttachment(String filename) throws Exception {
        BodyPart messageBodyPart = new MimeBodyPart();
        DataSource source = new FileDataSource(filename);
        messageBodyPart.setDataHandler(new DataHandler(source));
        messageBodyPart.setFileName(filename);
   
        _multipart.addBodyPart(messageBodyPart);
      }
   
      @Override
      public javax.mail.PasswordAuthentication getPasswordAuthentication() {
        return  new javax.mail.PasswordAuthentication(_user,_pass);
      }
   
      private Properties _setProperties() {
        Properties props = new Properties();
   
        props.put("mail.smtp.host", _host);
   
        if(_debuggable) {
          props.put("mail.debug", "true");
        }
   
        if(_auth) {
          props.put("mail.smtp.auth", "true");
        }
   
        props.put("mail.smtp.port", _port);
        props.put("mail.smtp.socketFactory.port", _sport);
        props.put("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory");
        props.put("mail.smtp.socketFactory.fallback", "false");
   
        return props;
      }
   
      // the getters and setters
      public String getBody() {
        return _body;
      }
   
      public void setBody(String _body) {
        this._body = _body;
      }

    public String[] get_to() {
        return _to;
    }

    public void set_to(String[] _to) {
        this._to = _to;
    }

    public String get_from() {
        return _from;
    }

    public void set_from(String _from) {
        this._from = _from;
    }

    public String get_subject() {
        return _subject;
    }

    public void set_subject(String _subject) {
        this._subject = _subject;
    }
   
    }


Step-4

in your Main class

public class GMailMain extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.main);

        Button addImage = (Button) findViewById(R.id.send);
        addImage.setOnClickListener(new View.OnClickListener() {
            public void onClick(View view) {
               
               
                GMailSender mailsender = new GMailSender("sender@gmail.com", "password123");

                String[] toArr = { "receiver1@gmail.com", "receiver2@gmail.com" };
                mailsender.set_to(toArr);
                mailsender.set_from("sender@gmail.com");
                mailsender.set_subject("This is an email sent using my Mail JavaMail wrapper from an Android device.");
                mailsender.setBody("Email body.");

                try {
                    //mailsender.addAttachment("/sdcard/filelocation");

                    if (mailsender.send()) {
                        Toast.makeText(GMailMain.this,
                                "Email was sent successfully.",
                                Toast.LENGTH_LONG).show();
                    } else {
                        Toast.makeText(GMailMain.this, "Email was not sent.",
                                Toast.LENGTH_LONG).show();
                    }
                } catch (Exception e) {
                   
                    Log.e("MailApp", "Could not send email", e);
                }
            }
        });

    }
}