Reverse-lookup questions

[TomJmac]

I want to install a snow leopard server at my home office in order to bring us up to date and give us all the collaboration services and backed up file storage that I feel we now need to be using. However, I’m confused about some of the dns aspects – and I wonder if anyone here has experience of a similar situation, or ideas on how I should be organising this.

I’ve had a broadband account from a large UK ISP for many years that gives me a static public IP, and my personal email address (me@bigisp.com) that I’ve used for the same long time. They actually give me a hostname at their site, that then allows me to have unlimited email addresses against that hostname. The ISP is Demon Internet.

I also have a domain for my business that is hosted by an entirely separate company. (They host domains at a much better price than my ISP does). Essentially they host my business website and they also forward / point any incoming business emails (addressed to anyone@mybusiness.com) to my static public IP.
This host company have setup mx records so that my in-house mail server is the primary mail server and they run a couple of backup mail servers at their offices as well, in case mine goes off line.

My router in the office (with the static IP) is configured to port-forward these incoming business emails to my old but reliable G3 mail server – and all is working well on the current network. I have several client computers and printers on this network.

Now as I understand things, I need to make sure that lookups AND reverse lookups are both configured for my domain before I can hope to get my dns (and external access to my internal network server services) functioning correctly?
When I check lookups online against (mail.mybusiness.com) or (calendar.mybusiness.com) the results come back with my public static IP address – which is good. However, when I do reverse lookups against my public IP – this always resolves to the email address hostname provided by (bigisp.com). I know they’ve allocated me an IP from a large range of IPs that they have so this seems to be an expected result.

Q1 – who should I ask to deal with changing the reverse PTR for my domain?
Q2 – should I ask them to change it for the domain (mybusiness.com) OR to change it for each individual host on that domain that I’m likely to be using (ichat.mybusiness.com), (calendar.mybusiness.com), (etc)?
Q3 – Assuming that I can get whoever it is to agree these changes, is the PTR adjustment likely to stop me receiving emails at my personal (me@bigisp.com) email account?

Sorry if I’ve popped this post into the wrong forum – also sorry if it’s a bit long, just trying to give good background.?

Thanks for any advice.

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