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

GmailBackground是一个小型库，可以在后台发送电子邮件，无需用户交互:

用法:

    BackgroundMail.newBuilder(this)
            .withUsername("username@gmail.com")
            .withPassword("password12345")
            .withMailto("toemail@gmail.com")
            .withType(BackgroundMail.TYPE_PLAIN)
            .withSubject("this is the subject")
            .withBody("this is the body")
            .withOnSuccessCallback(new BackgroundMail.OnSuccessCallback() {
                @Override
                public void onSuccess() {
                    //do some magic
                }
            })
            .withOnFailCallback(new BackgroundMail.OnFailCallback() {
                @Override
                public void onFail() {
                    //do some magic
                }
            })
            .send();

配置:

repositories {
    // ...
    maven { url "https://jitpack.io" }
 }
 dependencies {
            compile 'com.github.yesidlazaro:GmailBackground:1.2.0'
    }

权限:

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
<uses-permission android:name="android.permission.INTERNET"/>

对于附件，你需要设置READ_EXTERNAL_STORAGE权限:

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

源

(我自己测试过)

无法连接到SMTP主机: Smtp.gmail.com，端口:465

在清单中添加这一行:

<uses-permission android:name="android.permission.INTERNET" />

 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;
  }  


   }

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”)

要加附件，别忘了加。

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);