How does the internet work? Well, aside from the tubes, there's the DNS - Domain Name Service. Someone holds all the TLD's - Top Level Domains - such as .com, .uk, and so forth. And we 'buy' names off of DNS registers (I use BulkRegister.com). However, we need to find someone to host DNS entries for us. NOT webspace, just someone to actually hold our DNS entry. In my case, Prominic.net do my Domino hosting and my DNS hosting - so I just get them to do it all for me. (And they're very good)
So this DNS stuff. What is it ? Its a 'name' - such as billbuchan.com - that resolves to an IP address. My server(s) have static IP addresses on the internet, making like a bit easier, so all I need to do is point billbuchan.com to the public IP address of my server. However, there are more than one type of record. There's the 'Host' record - for web traffic - which tells your browser where to go. And there's the MX (Mail Exchange) record, which tells your eMail where to go.
In my case, I have Postini spam-scanning my stuff, so the mail goes there first, and then ends up at my server. A good example of web going direct to my server, and mail taking a more indirect route.
Now, theres a new-ish thing on the anti-spam thing called 'SPF' (short for Sender Policy Framework). This means that my DNS entries has some extra text entries, which state that mail has to come from a particular place. This *should* cut down the amount of spam that appears to come from my eMail servers (I hope).
One really useful site (And the point to this entire post!) was to point you at mxTookbox.com which gives you the tools to query MX records, and to create valid SPF records for your domains.
Phew. And you thought that hosting a service just meant slapping a server onto the internet, and switching it on, eh ?