fqdn = fully qualified domain name.
If you have console access to the server then you can run, "netstat -lpn | grep 143". This will tell you what daemon is listening on port 143 (this is the usual port for the IMAP daemon.
I am running Cyrus for my IMAP daemon and it looks like this. (note that mine is on the non standard port 142 because I have an IMAP proxy on 143. Just ignore this and stick with port 143). This also tells you what IP address(s) the daemon is listening on.
root@blaze:~# netstat -lpn | grep 142
tcp 0 0 127.0.0.1:142 0.0.0.0:* LISTEN 2031/cyrmaster