15,000 ain't massive

-though you would have to divide that into the size
let's see this account has 214,743 (and I know there's plenty of people who can beat that)
-of course most of that could be a lot less if I didn't have so many damn log file summaries to review...why they can't be thrown into something like splunk or another logfile aggregation database for viewing at my pleasure when needed I don't know...
I was gonna say you could always use a thick-client to transfer the entirety of folders, or zmmailbox to rename folders, but guess your past that.