Well, I also posted about the issue on WHT, so save me typing the background, I'll copy/paste it here:
Okay, so I've just set up Virtualmin and Webmin on my VPS (with a few tweaks from my VPS provider). I've tried sending a test email to the aliases that Vmin sets up, as well as an actual account. All I get back is an error saying that the address couldn't be found.
I sent a ticket to my VPS provider and he said that I need to set up an MX record to point to my VPS to receive mail (which I hadn't done because I thought I didn't need one, seeing as web, mail and DNS are all on the same server).
When I set up DNS with Webmin, I followed the guide here: http://forums.devshed.com/dns-36/set...in-406190.html
So, as I'd set up 'mail.holiday-ideas.org.uk' in Webmin/BIND as an A record and as a mail server record, I thought that would be sufficient.
Presumably, my VPS provider is suggesting that I set up 'mail.holiday-ideas.org.uk' as an MX record with my domain at my domain registrar's control panel (1&1)?
What I don't understand is why, when I was on a shared hosting account with another host, I could just register domains, point their nameservers to the ones my host supplied and then just host sites and mail for those domains without having to deal with MX records. What is different in this situation?