UPDATE: This looks to be a problem caused by my old install after all. Stopped Mailscanner and everything still worked.
I've upgraded to th latest non-NE version this week and noticed the following showing in zimbra.log:
Does anyone know where the MailScanner settings are so that I can have a look at what might be wrong...MailScanner: None of the files matched by the "Monitors For ClamAV Updates" patterns exist!
Does zimbra still use MailScanner in the first place? Just wondering if it was my old packages on the server from my original dovecot install, but chkconfig is reporting that those old packages are not configured to run.