Can You Tell If People Are Having Fun Over The Internet?

As I posted about here, I had been toying with GMing a new game.  Well it has come to fruition.  My group has started a PBEM (play by e-mail) game, set in the world of Robin Hobb's Farseer books. We've only been going for about 2 weeks now, which isn't very long in PBEM time, but I'm already having doubts.  The problem is, I can't tell if my players are having any fun. The start of an adventure