I populated a mailbox with 100,000 messages and accessed it using the new POP server and I've gotta say, it was pretty darn snappy. The only perceptible pause is on opening the mailbox, I would call it 500 to 1000 milliseconds (I didn't time it though). When you consider the latency you'd encounter in a typical client/server scenario... well, I think it's safe to say the e-mail server will be Fast Enough under reasonable (and often, highly unreasonable!) circumstances.