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.

You might find help here on the Citadel support forums:
http://uncensored.citadel.org/

I figured out the issue - I had to open ports 8080 and 4343 in my firewall since I specified these for Citadel.

I've added a suggestion that this is added to the email guide as it's easy for a new user like myself to overlook something like this!

Ok, I see now, well if it's to run the web ui you might want to keep it behind the firewall and use an SSH tunnel to get in safely. Just a thought, the more stuff you can do admin wise with SSH tunnels (or a VPN) the better off you are.

I'll check that out once I figure out the MX Record stuff. I've set up the public/private keys for the server so it would make sense to continue trying to lock everything down as much as possible, thanks for the advice!