Admittedly, this is an issue that is a fringe, but thought I'd post it just in case.
Yesterday, I was working to configure a client's server to use mail journaling. Everything was going smooth until I went to edit a server configuration document to add the mail rule for a couple of servers. The Rules tab was missing. I was on the Admin client, so I tried it from the Notes client and the tab showed up. So I finished the configuration and went searching for the cause. I mean, wouldn't you want to administrator the server configurations from the Admin client??
Looking around, I quickly found a technote on this issue that appears to be a throwback to the “old” days of 6.5.4 / 7.0. Something in the design of the Domino directory changed and a field got left behind that causes this issue. This explains why I only saw this issue on some of the older servers and not the newer ones.
A quick agent to delete the field from the document (it's in the technote) and I can now manage the server configurations from the Admin client.