Dear all
I got a lot error in mailbox.log like below. And user sometimes can't fetch big emails with attachment via pop3 proxy.
I use telnet to simulate pop3 fetch behavior, the connection is broken after I issued RETR command for a while
Can anyone tell me how to resolve this issue?

2013-06-20 10:11:38,663 ERROR [Pop3SSLServer-26] [name=xyhan@xxx.com;ip=10.10.15.31;oip=10.10.15.16;] pop - Error detected by SSL subsystem, dropping connection:javax.net.ssl.SSLException: Received fatal alert: protocol_version
2013-06-20 10:11:39,660 ERROR [Pop3SSLServer-36] [name=haolih@xxx.com;ip=10.10.15.31;oip=10.10.15.16 ;] pop - Error detected by SSL subsystem, dropping connection:javax.net.ssl.SSLException: Received fatal alert: protocol_version