title: sending email on android using smtp and Gmail how to make it work
body: <p>i am creating android application that send email in background without user interaction i had downloaded the three .jar files as the examples said and added to the manifest file the permission of INTERNET .</p>
  
  <p>but the system display errors can anyone help me to fix this errors </p>
  
  <p>its my first time dealing with email application </p>
  
  <h1>logcat</h1>
  
  <pre><code>01-13 23:05:20.028: E/MailApp(4357): Could not send email
  01-13 23:05:20.028: E/MailApp(4357): android.os.NetworkOnMainThreadException
  01-13 23:05:20.028: E/MailApp(4357):    at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1133)
  01-13 23:05:20.028: E/MailApp(4357):    at java.net.InetAddress.lookupHostByName(InetAddress.java:385)
  01-13 23:05:20.028: E/MailApp(4357):    at java.net.InetAddress.getLocalHost(InetAddress.java:365)
  01-13 23:05:20.028: E/MailApp(4357):    at javax.mail.internet.InternetAddress.getLocalAddress(InternetAddress.java:517)
  01-13 23:05:20.028: E/MailApp(4357):    at javax.mail.internet.UniqueValue.getUniqueMessageIDValue(UniqueValue.java:99)
  01-13 23:05:20.028: E/MailApp(4357):    at javax.mail.internet.MimeMessage.updateMessageID(MimeMessage.java:2054)
  01-13 23:05:20.028: E/MailApp(4357):    at javax.mail.internet.MimeMessage.updateHeaders(MimeMessage.java:2076)
  01-13 23:05:20.028: E/MailApp(4357):    at javax.mail.internet.MimeMessage.saveChanges(MimeMessage.java:2042)
  01-13 23:05:20.028: E/MailApp(4357):    at javax.mail.Transport.send(Transport.java:117)
  01-13 23:05:20.028: E/MailApp(4357):    at com.devleb.emaildemoinbackground.GMailSender.send(GMailSender.java:105)
  01-13 23:05:20.028: E/MailApp(4357):    at com.devleb.emaildemoinbackground.MainActivity$1.onClick(MainActivity.java:36)
  01-13 23:05:20.028: E/MailApp(4357):    at android.view.View.performClick(View.java:4240)
  01-13 23:05:20.028: E/MailApp(4357):    at android.view.View$PerformClick.run(View.java:17721)
  01-13 23:05:20.028: E/MailApp(4357):    at android.os.Handler.handleCallback(Handler.java:730)
  01-13 23:05:20.028: E/MailApp(4357):    at android.os.Handler.dispatchMessage(Handler.java:92)
  01-13 23:05:20.028: E/MailApp(4357):    at android.os.Looper.loop(Looper.java:137)
  01-13 23:05:20.028: E/MailApp(4357):    at android.app.ActivityThread.main(ActivityThread.java:5103)
  01-13 23:05:20.028: E/MailApp(4357):    at java.lang.reflect.Method.invokeNative(Native Method)
  01-13 23:05:20.028: E/MailApp(4357):    at java.lang.reflect.Method.invoke(Method.java:525)
  01-13 23:05:20.028: E/MailApp(4357):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
  01-13 23:05:20.028: E/MailApp(4357):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
  01-13 23:05:20.028: E/MailApp(4357):    at dalvik.system.NativeStart.main(Native Method)
  </code></pre>
  
  <h1>MainActivity.java</h1>
  
  <pre><code>package com.devleb.emaildemoinbackground;
  
  
  import android.app.Activity;
  import android.os.Bundle;
  import android.util.Log;
  import android.view.View;
  import android.view.Window;
  import android.widget.Button;
  import android.widget.Toast;
  
  public class MainActivity extends Activity {
  
       @Override
          public void onCreate(Bundle savedInstanceState) {
              super.onCreate(savedInstanceState);
              requestWindowFeature(Window.FEATURE_NO_TITLE);
              setContentView(R.layout.activity_main);
  
              Button addImage = (Button) findViewById(R.id.btn);
              addImage.setOnClickListener(new View.OnClickListener() {
                  public void onClick(View view) {
  
  
                      GMailSender mailsender = new GMailSender("sender@gmail.com", ".........");
  
                      String[] toArr = { "receiver@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(MainActivity.this,
                                      "Email was sent successfully.",
                                      Toast.LENGTH_LONG).show();
                          } else {
                              Toast.makeText(MainActivity.this, "Email was not sent.",
                                      Toast.LENGTH_LONG).show();
                          }
                      } catch (Exception e) {
  
                          Log.e("MailApp", "Could not send email", e);
                      }
                  }
              });
  
          }
      }
  </code></pre>
  
  <h1>GmailSender.java</h1>
  
  <pre><code>package com.devleb.emaildemoinbackground;
  
  
  
  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 = "sender@gmail.com"; // username
          _pass = "..........."; // password
          _from = "receive@gmail.com"; // email sent from
          _subject = ""; // email subject
          _body = "test email message sended!!"; // 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("") &amp;&amp; !_pass.equals("") &amp;&amp; _to.length &gt; 0 &amp;&amp; !_from.equals("") &amp;&amp; !_subject.equals("") &amp;&amp; !_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 &lt; _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;
      }
  
      }
  </code></pre>