b2c购物网站系统软文写作的三个要素

要检测邮箱是否真实存在，必须了解两方面知识：
1. MX记录，winodws的nslookup命令。 查看学习

2. SMTP协议，如何通过telnet发送邮件。查看学习

有个网站可以校验，http://verify-email.org/， 不过一小时只允许验证10次。

代码如下（补充了一些注释）：

import java.io.IOException;import org.apache.commons.net.smtp.SMTPClient;
import org.apache.commons.net.smtp.SMTPReply;
import org.apache.log4j.Logger;
import org.xbill.DNS.Lookup;
import org.xbill.DNS.Record;
import org.xbill.DNS.Type;/*** * 校验邮箱：1、格式是否正确 2、是否真实有效的邮箱地址* 步骤：* 1、从dns缓存服务器上查询邮箱域名对应的SMTP服务器地址* 2、尝试建立Socket连接* 3、尝试发送一条消息给SMTP服务器* 4、设置邮件发送者* 5、设置邮件接收者* 6、检查响应码是否为250(为250则说明这个邮箱地址是真实有效的)* @author Michael Ran**/
public class CheckEmailValidityUtil {private static final Logger logger = Logger.getLogger(CheckEmailValidityUtil.class);/*** @param email 待校验的邮箱地址* @return*/public static boolean isEmailValid(String email) {if (!email.matches("[\\w\\.\\-]+@([\\w\\-]+\\.)+[\\w\\-]+")) {logger.error("邮箱（"+email+"）校验未通过，格式不对!");return false;}String host = "";String hostName = email.split("@")[1];//Record: A generic DNS resource record. The specific record types //extend this class. A record contains a name, type, class, ttl, and rdata.Record[] result = null;SMTPClient client = new SMTPClient();try {// 查找DNS缓存服务器上为MX类型的缓存域名信息Lookup lookup = new Lookup(hostName, Type.MX);lookup.run();if (lookup.getResult() != Lookup.SUCCESSFUL) {//查找失败logger.error("邮箱（"+email+"）校验未通过，未找到对应的MX记录!");return false;} else {//查找成功result = lookup.getAnswers();}//尝试和SMTP邮箱服务器建立Socket连接for (int i = 0; i < result.length; i++) {host = result[i].getAdditionalName().toString();logger.info("SMTPClient try connect to host:"+host);//此connect()方法来自SMTPClient的父类:org.apache.commons.net.SocketClient//继承关系结构：org.apache.commons.net.smtp.SMTPClient-->org.apache.commons.net.smtp.SMTP-->org.apache.commons.net.SocketClient//Opens a Socket connected to a remote host at the current default port and //originating from the current host at a system assigned port. Before returning,//_connectAction_() is called to perform connection initialization actions. //尝试Socket连接到SMTP服务器client.connect(host);//Determine if a reply code is a positive completion response（查看响应码是否正常）. //All codes beginning with a 2 are positive completion responses（所有以2开头的响应码都是正常的响应）. //The SMTP server will send a positive completion response on the final successful completion of a command. if (!SMTPReply.isPositiveCompletion(client.getReplyCode())) {//断开socket连接client.disconnect();continue;} else {logger.info("找到MX记录:"+hostName);logger.info("建立链接成功："+hostName);break;}}logger.info("SMTPClient ReplyString:"+client.getReplyString());String emailSuffix="163.com";String emailPrefix="ranguisheng";String fromEmail = emailPrefix+"@"+emailSuffix; //Login to the SMTP server by sending the HELO command with the given hostname as an argument. //Before performing any mail commands, you must first login. //尝试和SMTP服务器建立连接,发送一条消息给SMTP服务器client.login(emailPrefix);logger.info("SMTPClient login:"+emailPrefix+"...");logger.info("SMTPClient ReplyString:"+client.getReplyString());//Set the sender of a message using the SMTP MAIL command, //specifying a reverse relay path. //The sender must be set first before any recipients may be specified, //otherwise the mail server will reject your commands. //设置发送者，在设置接受者之前必须要先设置发送者client.setSender(fromEmail);logger.info("设置发送者 :"+fromEmail);logger.info("SMTPClient ReplyString:"+client.getReplyString());//Add a recipient for a message using the SMTP RCPT command, //specifying a forward relay path. The sender must be set first before any recipients may be specified, //otherwise the mail server will reject your commands. //设置接收者,在设置接受者必须先设置发送者，否则SMTP服务器会拒绝你的命令client.addRecipient(email);logger.info("设置接收者:"+email);logger.info("SMTPClient ReplyString:"+client.getReplyString());logger.info("SMTPClient ReplyCode："+client.getReplyCode()+"(250表示正常)");if (250 == client.getReplyCode()) {return true;}} catch (Exception e) {e.printStackTrace();} finally {try {client.disconnect();} catch (IOException e) {}}return false;}public static void main(String[] args) {System.out.println(isEmailValid("903109360@qq.com"));}
}

执行结果：

MX record about qq.com exists.
Connection succeeded to mx3.qq.com.
220 newmx21.qq.com MX QQ Mail Server
>HELO 163.com
=250 newmx21.qq.com
>MAIL FROM: <163.com@ranguisheng>
=250 Ok
>RCPT TO: <903109360@qq.com>
=250 Ok

Outcome: true

如果将被验证的邮箱换为：903109360@qq.con，就会验证失败：

找不到MX记录
Outcome: false

值得注意的是犹豫校验的第一步是从DNS服务器查询MX记录 所以必须联网  否则校验会失效 因为找不到MX记录会导致真实的有效地址也校验为无效 这点要特别注意。

此代码需要两个jar包：

1、Apache Commons Net  

maven地址：http://mvnrepository.com/artifact/commons-net/commons-net/

2、dnsjava

maven地址：http://mvnrepository.com/artifact/dnsjava/dnsjava/

PS:目前还没发验证部分企业邮箱，后面想办法解决这个问题之后更新此文章。

相关资源下载>>>：

dnsjava下载

Apache-commons-net下载 

参考文档：

apache-commons-net API

dnsjava API