To be honest, if your here asking questions like "whats an MX record" i really dont think you should be trying to run an e-mail server..... With that being said, you need to host your DNS somewhere (theres plenty of places that will do this free, just do a google) in the DNS record you will have the ability to set your MX record. I would recommend running your server as a fully fledged web server, and point the A record to it too....
Do you have 2 telephone lines? i dont think its possible to run 2 adsl services on 1 line (but i stand to be corrected
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