Help with setting up Citadel (Debian 6 Squeeze)

I've followed the guide for setting up Citadel but I am having difficulty getting to the web interface. My Linode is also running apache so I've set up Citadel on ports 8080 and 4343 as instructed in the guide. When I navigate to mail.domain.com though it just shows what is at domain.com.

I suspect there may be a problem with my hostname setup. I'm new to Linux and I've been following the awesome guide provided by Linux. At this stage my hostname is just 'starkbox' and even when I add the -f flag to find the FQDN it still just responds with 'starkbox'. I have the DNS set up though to point my domain.com towards the Linode and that works fine.

So could someone please explain to me what I need to do with my hostname and hosts files and if I need to make any changes in my DNS settings? My aim is to be able to send/receive emails using @domain.com instead of @mail.domain.com.