I am curious too. For our larger implementation, we use Communigate from Stalker, we have 700,000 mailboxes and they in fact recommend using NAS over NFS (we currently use iSCSI and SCSI). It may be because we use Solaris on that server and (since Sun invented NFS in the first place) they have pretty good NFS implementation.
But I would really like to know more information about why not NFS, if it is a server or client issue, etc. For example we have our storage server running Solaris, so if it is a Linux NFS server issue, it should be no problem.
I am elaborating if I should keep our mailstore on NFS.
We have also one installation of Zimbra NE and I'm considering using Hierarchical Storage Management feature to move older data to NFS to our big storage...
Do you know who wrote that statement? Did someone just try it once, it did not work so you don't recommend it or there was some kind of research?