NOTE: The subject line is supposed to read: "rPath ZCS - no NTP server workaround"
So it doesn't appear that the 4.5.4 rPath Zimbra installation has ntp compiled. Nor does it have half of the pre-reqs for compiling ntp. The reason this was an issue was because the virtual machine would slowly, over the course of a couple days, fall out of sync with "real-time." Users started complaining that they were getting emails from "the future."
Instead of busting my head on this I came up with the following solution bred from a backup script. I had a public key relationship set up one way, Zimbra to an OSX Server, to push backup files. I decided to reciprocate that to resolve my date/time problem.
In short, I set up public key authentication from the OSX server to the rPath installation, and set cron on the OSX server to run the following script every hour. It has been working great for the past two weeks so I felt I'd share.
# Sets the date on the rPath Zimbra installation.
# This supplements the installation as ntp was not
# compiled with the full installation so we keep
# losing the time.
# Written by Mike Wyant. July 1, 2007
ssh "$USER"@"$REMOTE" date $DATE