Smulkin turned off the email functionality a while back to counteract spammers.
Thank you, Jamie - you nailed it!
Yep - we had a slew of spammers using that feature to the point that it was affecting site performance. The "most online" figure (in the Who's Online box in the upper left) reflects the day it peaked and we killed it off to keep the site stable and page loads fast. Since the Private Messaging is enabled the overall impact among members was minimal.