I had a client very unhappy last week when I failed to respond in a timely manner to his emails. The problem was simple enough: I hadn't received them! It seems that my iMac's Mail.app was having some serious problems, but didn't let anyone know. After shutting down Mail.app, then forcing it to shutdown, checking the disk integrity, and restarting mail, it's discovering all sorts of email out there it forgot to tell me about. It's been running for about ten minutes and is still finding email, up to 342 unread messages so far. So, if you think I'm ignoring your email, it's possible that I just haven't seen it yet.