Exchange on SBS 2000 Server

I had to reload my W2K SBS, including Exchange. When I open Outlook 2003 on my XP Pro client, I receive a message that “Exchange is currently in recovery mode”, but I still receive email messages. Also, now I cannot send email to my internal employees. What is recovery mode, and why is it telling me this? I have some W2K clients that when they go to launch Outlook they receive a message that says the Exchange server is not available. What am I missing and how can I get this fixed quick?