64bit is something we'll get too. RHEL3 is a no go. It runs the older kernel and we do not have any plans to allow folks to install new mail servers on such an old OS. IMHO is much better for us to lean forward on OS support than try to back port to OS's that are years old. Lucky for you the code is open source so if you *must* support such environment you can port it yourself. Zimbra however doesn't plan to port or support it. SLES10 we will support. As you know we already support ES9. Funny that you ask us to go back in time on Red Hat but forward on SuSE
Cake and eat it too?