您可以将.eml转换为javax.mail.Messages mailMessage：
Loading .eml files into javax.mail.Messages
然后你可以使用这个库在MessageBean中进行转换：
http://javaclue.blogspot.com/2009/09/portable-java-mail-message-bean_02.html
MessageBean mb = MessageBeanUtil.mimeToBean（mailMessage）;

锁定，本次有disputes about this answer’s content正在解析。它目前不接受新的交互。

Javamail可以读取EML文件。

import java.util.*;
import java.io.*;
import javax.mail.*;
import javax.mail.internet.*;

public class ReadEmail {

   public static void main(String args[]) throws Exception{
       display(new File("C:\\temp\\message.eml"));

   }

   public static void display(File emlFile) throws Exception{
        Properties props = System.getProperties();
        props.put("mail.host", "smtp.dummydomain.com");
        props.put("mail.transport.protocol", "smtp");

        Session mailSession = Session.getDefaultInstance(props, null);
        InputStream source = new FileInputStream(emlFile);
        MimeMessage message = new MimeMessage(mailSession, source);

        System.out.println("Subject : " + message.getSubject());
        System.out.println("From : " + message.getFrom()[0]);
        System.out.println("--------------");
        System.out.println("Body : " +  message.getContent());
    }
}