Courier-imap with sendmail setup: why is my IMAP inbox empty?

I've successfully installed sendmail, but when I connect to the Courier IMAP server via Outlook, the Inbox is listed as empty. When I check the inbox with Alpine locally on the server, it has content though. Why? I do see files with content in /var/mail . Is that not where Courier-imap checks for mail? The setup is pretty clean - I run Ubuntu 12.04 on AWS, have installed sendmail and courier-imap. sendmail was configured with sendmailconfigure and it works well to both send and receive mail. The problem is with courier.