Add jar files mail.jar,activation.jar,additionnal.jar

 String sub="Thank you for your online registration" ; 
 Mail m = new Mail("emailid", "password"); 

 String[] toArr = {"ekkatrainfo@gmail.com",sEmailId};
 m.setFrom("ekkatrainfo@gmail.com"); 

     m.setTo(toArr);
     m.setSubject(sub);
    m.setBody(msg);



                     try{


                            if(m.send()) { 

                            } else { 

                            } 
                          } catch(Exception e) { 

                            Log.e("MailApp", "Could not send email", e); 
                          } 

  package com.example.ekktra;

   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.PasswordAuthentication;
   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 Mail 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 Mail() { 
      _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 Mail(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 PasswordAuthentication getPasswordAuthentication() { 
     return new 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 void setTo(String[] toArr) {
     // TODO Auto-generated method stub
    this._to=toArr;
 }

public void setFrom(String string) {
    // TODO Auto-generated method stub
    this._from=string;
}

 public void setSubject(String string) {
    // TODO Auto-generated method stub
    this._subject=string;
  }  


   }

您可以使用JavaMail API来处理电子邮件任务。JavaMail API可以在JavaEE包中获得，它的jar可以下载。遗憾的是，它不能直接在Android应用程序中使用，因为它使用的AWT组件在Android中完全不兼容。

你可以在以下位置找到JavaMail的Android端口: http://code.google.com/p/javamail-android/

将jar添加到应用程序并使用SMTP方法

为了帮助那些获得网络主线程异常与SDK目标>9。这是使用droopie的代码上面，但将类似于任何工作。

StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();

StrictMode.setThreadPolicy(policy); 

android.os.NetworkOnMainThreadException

您可以如下所示使用AsyncTask

public void onClickMail(View view) {
    new SendEmailAsyncTask().execute();
}

class SendEmailAsyncTask extends AsyncTask <Void, Void, Boolean> {
    Mail m = new Mail("from@gmail.com", "my password");

    public SendEmailAsyncTask() {
        if (BuildConfig.DEBUG) Log.v(SendEmailAsyncTask.class.getName(), "SendEmailAsyncTask()");
        String[] toArr = { "to mail@gmail.com"};
        m.setTo(toArr);
        m.setFrom("from mail@gmail.com");
        m.setSubject("Email from Android");
        m.setBody("body.");
    }

    @Override
    protected Boolean doInBackground(Void... params) {
        if (BuildConfig.DEBUG) Log.v(SendEmailAsyncTask.class.getName(), "doInBackground()");
        try {
            m.send();
            return true;
        } catch (AuthenticationFailedException e) {
            Log.e(SendEmailAsyncTask.class.getName(), "Bad account details");
            e.printStackTrace();
            return false;
        } catch (MessagingException e) {
            Log.e(SendEmailAsyncTask.class.getName(), m.getTo(null) + "failed");
            e.printStackTrace();
            return false;
        } catch (Exception e) {
            e.printStackTrace();
            return false;
        }
    }

我为其他需要帮助的人找到了一个更短的选择。代码是:

package com.example.mail;

import java.util.Properties;

import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;

public class SendMailTLS {

    public static void main(String[] args) {

        final String username = "username@gmail.com";
        final String password = "password";

        Properties props = new Properties();
        props.put("mail.smtp.auth", "true");
        props.put("mail.smtp.starttls.enable", "true");
        props.put("mail.smtp.host", "smtp.gmail.com");
        props.put("mail.smtp.port", "587");

        Session session = Session.getInstance(props,
          new javax.mail.Authenticator() {
            protected PasswordAuthentication getPasswordAuthentication() {
                return new PasswordAuthentication(username, password);
            }
          });

        try {

            Message message = new MimeMessage(session);
            message.setFrom(new InternetAddress("from-email@gmail.com"));
            message.setRecipients(Message.RecipientType.TO,
                InternetAddress.parse("to-email@gmail.com"));
            message.setSubject("Testing Subject");
            message.setText("Dear Mail Crawler,"
                + "\n\n No spam to my email, please!");

            Transport.send(message);

            System.out.println("Done");

        } catch (MessagingException e) {
            throw new RuntimeException(e);
        }
    }
}

来源:通过JavaMail API发送电子邮件

希望这能有所帮助!好运！

如果使用“smtp.gmail.com”作为默认的smtp服务器，请注意。

谷歌将迫使您更改您的链接电子邮件帐户密码频繁由于他们过于热心的“可疑活动”政策。本质上，它将短时间内来自不同国家的重复smtp请求视为“可疑活动”。因为他们假设你(电子邮件账户持有人)一次只能在一个国家。

当谷歌系统检测到“可疑活动”时，它将阻止进一步的电子邮件，直到您更改密码。因为你已经将密码硬编码到应用程序中，每次发生这种情况，你都必须重新发布应用程序，这并不理想。这种情况发生在一周内3次对我来说，我甚至存储密码在另一个服务器上，每次谷歌强迫我更改密码时，我都动态地获取密码。

因此，我建议使用许多免费的smtp提供商之一，而不是“smtp.gmail.com”，以避免这个安全问题。使用相同的代码，但将“smtp.gmail.com”更改为新的smtp转发主机。

我无法运行维纳亚克B的代码。最后我解决了这个问题如下:

1.使用这个

2.使用AsyncTask。

3.更改发件人gmail帐户的安全问题。(更改为“TURN ON”)