It's easy. If you have 1 single ip address for your name servers you can disable the dns service in ispconfig and use the godaddy dns.
- In the A(host) TAB add
server xxx.xxx.xxx.xxx (here your server ip address)
mail xxx.xxx.xxx.xxx (here your mail server ip address)
- In the cname(alias) TAB add
- In the MX (Mail Exchanger) TAB
10 @ mail.yourdomain.com
That's all. You can add more alias if you want and A records for others servers in your domains.