java mail: set

Problem: email thread is hanging at socket read
Today we found a email problem in production, all of the mail threads (3 threads) are hanging/sitting/blocking at same point
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(SocketInputStream.java:129)
at java.io.BufferedInputStream.fill(BufferedInputStream.java:218)
at java.io.BufferedInputStream.read(BufferedInputStream.java:237)
- locked <0x9698d6c0> (a java.io.BufferedInputStream)
at com.sun.mail.util.LineInputStream.readLine(LineInputStream.java:56)
at com.sun.mail.smtp.SMTPTransport.readServerResponse(SMTPTransport.java:757)
at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:673)
at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:168)
at javax.mail.Service.connect(Service.java:227)
at javax.mail.Service.connect(Service.java:131)
at javax.mail.Service.connect(Service.java:87)
at com.sun.mail.smtp.SMTPTransport.connect(SMTPTransport.java:105)
- locked <0x9698d6e0> (a com.sun.mail.smtp.SMTPTransport)
at javax.mail.Transport.send0(Transport.java:162)
at javax.mail.Transport.send(Transport.java:80) 
I search the "javax.mail.Transport.send" and "com.sun.mail.smtp.SMTPTransport.readServerResponse", got no hits.
while my colleague get answer from internet. 
http://jira.sakaiproject.org/browse/KNL-96
http://forums.sun.com/thread.jspa?forumID=43&threadID=474662
"I have a servlet which uses JavaMail to send out emails to a smtp server. During our peak access hours, we have many requests to send out emails, after a while my application went into CLOSE WAIT accumulation and finally my application server stops processing."
"ExecuteThread: '11' for queue: 'default'" daemon prio=5 tid=0x39fb28 nid=0x18 runnable [0xbf980000..0xbf981a38]
at java.net.SocketInputStream.socketRead(Native Method)
at java.net.SocketInputStream.read(SocketInputStream.java:85)
at java.io.BufferedInputStream.