I'm having a problem attempting to move a large mailbox from one Zimbra server to another (ZCS 5.0.9) using imapsync. The imapsync appears to be failing on the same message (a large file) on every attempt.

I believe from the below logs that the Zimbra SessionCache is timing out the session because it has seen no new commands even though the Zimbra IMAP library is continuing to transfer data...
2009-07-24 11:04:09,288 INFO  [Timer-3] [] SessionCache - Removed 1 idle sessions (IMAP). 34 active sessions remain.
2009-07-24 11:04:09,307 INFO  [ImapSSLServer-27510] [] ProtocolHandler - Exception occurred while handling connection
java.net.SocketException: Socket is closed
        at com.sun.net.ssl.internal.ssl.SSLSocketImpl.checkEOF(SSLSocketImpl.java:1223)
        at com.sun.net.ssl.internal.ssl.SSLSocketImpl.checkWrite(SSLSocketImpl.java:1244)
        at com.sun.net.ssl.internal.ssl.AppOutputStream.write(AppOutputStream.java:43)
        at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:65)
        at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:123)
        at com.zimbra.cs.imap.ImapHandler.fetch(ImapHandler.java:3065)
        at com.zimbra.cs.imap.ImapHandler.doFETCH(ImapHandler.java:2872)
        at com.zimbra.cs.imap.ImapHandler.executeRequest(ImapHandler.java:423)
        at com.zimbra.cs.imap.TcpImapHandler.processCommand(TcpImapHandler.java:124)
        at com.zimbra.cs.tcpserver.ProtocolHandler.processConnection(ProtocolHandler.java:160)
        at com.zimbra.cs.tcpserver.ProtocolHandler.run(ProtocolHandler.java:128)
        at EDU.oswego.cs.dl.util.concurrent.PooledExecutor$Worker.run(Unknown Source)
        at java.lang.Thread.run(Thread.java:595)
I have run imapsync in debug mode and the server is clearly continuing to transfer the message until the socket is closed by the SessionCache underneath it.

Does anyone know of any variables that I can tweak to extend the session cache timeout for IMAP connections?

-- Greg