[Exim] qualify_domain

How will you fill-up "qualify_domain" in /exim.conf

    (1) I have not registered a domain_name

    (2) I have a dial-up connection with an ISP. I use the email_id
    given by him as my emailaddress,

    (3) I have also a cable modem connection with another ISP. For
    receiving mails, I use the hostname given by the the ISP in
    (2).For sending mails, I use the IP address given by the ISP in
    (3)

     Thanks. Ramachandran