POP3 and IMAP won't communicate with RC2. They do not send something the java modules in Zimbra expect and it tosses a null pointer exception, which is pretty fatal to the login/authendication process.
On the Thunderbird side the connection goes dead but does not toss any error for the longest time. If you watch the zimbra logs you'll see these sorts of errors:
Code:
2007-12-18 14:40:13,847 INFO [Pop3SSLServer-744] [ip=209.147.114.202;] pop - connected
2007-12-18 14:40:13,910 INFO [Pop3SSLServer-744] [] ProtocolHandler - Exception occurred while handling connection
java.lang.NullPointerException
at com.zimbra.cs.pop3.Pop3Handler.doAUTH(Pop3Handler.java:508)
at com.zimbra.cs.pop3.Pop3Handler.processCommandInternal(Pop3Handler.java:235)
at com.zimbra.cs.pop3.Pop3Handler.processCommand(Pop3Handler.java:155)
at com.zimbra.cs.pop3.TcpPop3Handler.processCommand(TcpPop3Handler.java:46)
at com.zimbra.cs.tcpserver.ProtocolHandler.processConnection(ProtocolHandler.java:212)
at com.zimbra.cs.tcpserver.ProtocolHandler.run(ProtocolHandler.java:179)
at EDU.oswego.cs.dl.util.concurrent.PooledExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Thread.java:619)
2007-12-18 14:40:13,910 INFO [Pop3SSLServer-744] [] ProtocolHandler - Handler exiting normally
I don't recall the thread but I did see one of the Zimbra employees file a bug for this, and I think (think mind you) they fixed it pretty quickly, but I'm assuming that fix is in the GA version.