james内网邮件服务器收邮件问题？

我用James做了一个内网邮件系统，是通过数据库方式实现的，而且在inbox表添加了邮件状态字段，用来标记邮件的已读、未读和删除状态。能收发邮件，现在能收发邮件，但改变邮件状态（或者把该邮件删除）后，再去查收邮件会报异常，之后便不能对该用户（收件人）发送邮件了。请帮忙看看，谢谢！异常如下：
javax.mail.MessagingException: error getting UIDL;
  nested exception is:
        java.io.IOException: Unexpected response: .
        at com.sun.mail.pop3.POP3Folder.getUID(POP3Folder.java:429)
        at com.colordream.manager.impl.email.SendMailMangerImpl.getMail(SendMail
MangerImpl.java:139)
        at com.colordream.action.email.SendMailAction.getMailFromMethod(SendMail
Action.java:93)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.
java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAcces
sorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:585)
        at org.apache.struts.actions.DispatchAction.dispatchMethod(DispatchActio
n.java:270)
        at org.apache.struts.actions.DispatchAction.execute(DispatchAction.java:
187)
        at org.springframework.web.struts.DelegatingActionProxy.execute(Delegati
ngActionProxy.java:106)
        at org.apache.struts.action.RequestProcessor.processActionPerform(Reques
tProcessor.java:431)
        at org.apache.struts.action.RequestProcessor.process(RequestProcessor.ja
va:236)
        at org.apache.struts.action.ActionServlet.process(ActionServlet.java:119
6)
        at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(Appl
icationFilterChain.java:237)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationF
ilterChain.java:157)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperV
alve.java:214)
        at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValv
eContext.java:104)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.jav
a:520)
        at org.apache.catalina.core.StandardContextValve.invokeInternal(Standard
ContextValve.java:198)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextV
alve.java:152)
        at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValv
eContext.java:104)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.jav
a:520)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.j
ava:137)
        at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValv
eContext.java:104)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.j
ava:118)
        at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValv
eContext.java:102)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.jav
a:520)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineVal
ve.java:109)
        at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValv
eContext.java:104)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.jav
a:520)
        at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:929)        at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:16
0)
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java
:799)
        at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.proce
ssConnection(Http11Protocol.java:705)
        at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java
:577)
        at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadP
ool.java:683)
        at java.lang.Thread.run(Thread.java:595)
Caused by: java.io.IOException: Unexpected response: .
        at com.sun.mail.pop3.Protocol.simpleCommand(Protocol.java:374)
        at com.sun.mail.pop3.Protocol.uidl(Protocol.java:300)
        at com.sun.mail.pop3.POP3Folder.getUID(POP3Folder.java:423)
        ... 39 more