用mail.jar爬取邮件时报错Connection timed out: connect

String host = "app.mail";
String username = "xkesh@lkh.com.cn";
String password = "123456";

Properties props = new Properties();
Session session = Session.getDefaultInstance(props, null);

Store store = session.getStore("imap");
store.connect(host, username, password);

Folder folder = store.getFolder("INBOX");
folder.open(Folder.READ_ONLY);
Message message[] = folder.getMessages();
System.out.println("邮件数量:　" + message.length);
ShowMail re = null;
Exception in thread "main" javax.mail.MessagingException: Connection timed out: connect;
nested exception is:
java.net.ConnectException: Connection timed out: connect
at com.sun.mail.imap.IMAPStore.protocolConnect(IMAPStore.java:670)
at javax.mail.Service.connect(Service.java:295)
at javax.mail.Service.connect(Service.java:176)
at test.main(test.java:21)
Caused by: java.net.ConnectException: Connection timed out: connect
at java.net.DualStackPlainSocketImpl.connect0(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at com.sun.mail.util.SocketFetcher.createSocket(SocketFetcher.java:321)
at com.sun.mail.util.SocketFetcher.getSocket(SocketFetcher.java:237)
at com.sun.mail.iap.Protocol.<init>(Protocol.java:116)
at com.sun.mail.imap.protocol.IMAPProtocol.<init>(IMAPProtocol.java:115)
at com.sun.mail.imap.IMAPStore.newIMAPProtocol(IMAPStore.java:685)
at com.sun.mail.imap.IMAPStore.protocolConnect(IMAPStore.java:636)
... 3 more
我测试的是内网 163的我测过了可以就是内网的这样 求大神帮助