I have installed Procmail per the How to and updated Procmail to version 3.21 using the rpm from the Redhat site.
It appears to be working fine ie no server errors and the mail processing is happening. I had quite a bit of fun getting the procmailrc configuration right

I think my problem comes from some of the previous mistakes in the procmailrc file.
The problem I have is MS Outlook 2000 (SR1) is reporting an error (but mail is processed OK). The MS error is "Your server has reported a UID which does not comply with the IMAP standard....." Choosing the detail button gives -:
MsgSeqNum 1490, New UID 996997017. Prev UID: 996997028, Next UID: 0.
Account: LinuxServer
Protocol: IMAP
Server: 192.168.0.1
Port: 143
There are a large number of repetitions of the error dialog with different UIDs and the UIDs involved don't change each time the error dialogs appear.
How do I go about correcting the problem ?