JavaMail直接发送邮件

一般用JavaMail发送邮件都需要先登录到外部smtp服务器（如smtp.163.com） 二次转发，其实只要得到域名的邮件交换服务器地址(MX)就可以直接将邮件发出

这里用到了dnsjava（下载地址：http://www.dnsjava.org/）来获取MX记录。考虑到效率问题可将每次获取的MX记录保存到xml或数据库，下次使用是先检索本地数据，若不存在再获取其MX记录。

SendMail.java

import org.xbill.DNS.*;
import java.util.Properties;
import javax.mail.internet.*;
import javax.mail.*;
import javax.mail.Address;
import javax.mail.Message;
import javax.activation.*;

public class SendMail
...{
/** *//**
* @param mailFrom 发送者,任意值
* @param mailTo 接受者地址
* @param subject 主题
* @param content 内容
* @param filepath 附件
* @return 是否发送成功
*/
public static boolean send(String mailFrom, String mailTo, String subject, String content,
String[] filepath)
...{
if (!mailTo.matches("\w+([-_.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*")) ...{ //判断格式
return false;
}
try ...{
String hostName = mailTo.split("@")[1];
String host = null;

Lookup lookup = new Lookup(hostName, Type.MX); // 获取主机的MX记录
lookup.run();
if (lookup.getResult() != Lookup.SUCCESSFUL) ...{
return false;
}
else ...{
Record[] result = lookup.getAnswers();
host = result[0].getAdditionalName().toString(); // 这里只取第一个服务器
}

Properties prop = new Properties();
prop.put("mail.smtp.host", host);

Session ssn = Session.getInstance(prop, null);
//ssn.setDebug(true);
//System.setOut(new PrintStream(new File("sendlog.log")));
Address addressFrom = new InternetAddress(mailFrom, "Sender");
Address addressTo = new InternetAddress(mailTo, "Receiver");

MimeBodyPart messageBodyPart = new MimeBodyPart();
Multipart multipart = new MimeMultipart();

messageBodyPart.setText(content);
messageBodyPart.setHeader("content-type", "text/html");
multipart.addBodyPart(messageBodyPart);
DataSource source = null;

if (filepath != null) ...{ //添加附件
for (int i = 0; i < filepath.length; i++) ...{
messageBodyPart = new MimeBodyPart();
source = new FileDataSource(filepath[i]);
messageBodyPart.setDataHandler(new DataHandler(source));
messageBodyPart.setFileName(filepath[i]);
multipart.addBodyPart(messageBodyPart);
}
}

MimeMessage message = new MimeMessage(ssn);

message.setSubject(subject);
message.setFrom(addressFrom);
message.addRecipient(Message.RecipientType.TO, addressTo);
message.setContent(multipart);
message.saveChanges();

Transport tran = (Transport) ssn.getTransport("smtp");
tran.connect();
tran.sendMessage(message, message.getAllRecipients());
tran.close();
return true;
} catch (Exception e) ...{
//e.printStackTrace();
return false;
}
}
}
测试：

public class Test
...{
public static void main(String[] args)
...{
SendMail.send("MailFrom@YourDomain.Suffix", "MailTo@Domain.Suffix", "你好", "你好啊", null);
}
}
注意：有些邮件服务器会验证当前提交邮件的链接的IP，即是验证YourDomain.Suffix对应的IP记录是否和当前链接相同，所以如果发送方地址随便填写可能发送不成功