Primary Mail Server and a backup DNS server

Ok, here is my situation. I have a domain name 700R4.com and it is hosted with some company in new york (in california) and they host our site and our email. I want to setup a main server on my company network to handle all of our email, i dont want to use our host for the email.

How do I go about doing this? I will be running linux and apache. I dont want to buy exchange server so I need something for linux. I dont knwo what to use.

I also would like to have the same server used as a backup DNS for my sites, how can I do this with apache? I have several domains I would like to have back up DNS's for.

My connection will be an SDSL 1.5/1.5 and I only have one IP address.

Thanks.

I would not move the backup DNS to your site, but the primary. This makes you much more flexible if you want to change anything.
If your current ISP does not offer advanced DNS services, get in contact with a registrar like Godaddy and move only your domain there via KK. Keep the webspace where it is.

I am paying about $6/year for domain registration per year including backup DNS services
(I never used godaddy, so I can't tell anything about them, but the web hosting forum would probably help here)

You need to setup the DNS A record to point to to the californian machine and the MX record to point to your local one (MX=Mail eXchanger).
i.e.:
www.yourdomain.com -> 1.2.3.4 (california)
mail.yourdomain.com -> 9.8.7.6 (local, this is called a "glue" record)
MX mail.yourdomain.com

All major linux distributions come with all software you need installed by default:
sendmail / pop3d / imapd : Email
bind : DNS

But remember: Never connect a default installation to the internet without securing it first!

Apache is a http server though, you won't need it if you are not hosting the websites there too.

There is alternatives to these programs and there has been hot discussions which is better. Search this forum (DNS) for "tinydns" and "qmail" if you are curious.

The single IP address will limit you to use SSL on only ONE domain. Nothing else I can remember out of my head.

hth,
M.