javaMail异常 Unknown SMTP host 只在linux下异常

这是邮件发送的SMTP smtp.ym.163.com
是163的集团邮箱程序在windows下跑的是正常的
发送的邮件收到了但是一放到linux服务器上,就报如下异常
Caused by: java.net.UnknownHostException: smtp.ym.163.com
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:177)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)
at java.net.Socket.connect(Socket.java:529)
at java.net.Socket.connect(Socket.java:478)
at com.sun.mail.util.SocketFetcher.createSocket(SocketFetcher.java:233)
at com.sun.mail.util.SocketFetcher.getSocket(SocketFetcher.java:189)
at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:1359)
... 85 more
javax.mail.MessagingException: Unknown SMTP host: smtp.ym.163.com;
  nested exception is:
java.net.UnknownHostException: smtp.ym.163.com
at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:1389)
at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:412)
at javax.mail.Service.connect(Service.java:310)
at javax.mail.Service.connect(Service.java:169)
at javax.mail.Service.connect(Service.java:118)
at javax.mail.Transport.send0(Transport.java:188)
at javax.mail.Transport.send(Transport.java:118)
....