>My ISP want me to add the following lines to the DNS-part.
Why is that? Is your e-smith's DNS server public? Normally it is only an internal DNS for you own network so you don't need to put those lines in the config files...normally e-smith does that automatically.
In my case I added these lines to the configuration file of my public dns server. The public dns server for my domain is granitecanyon. But if you still need to put them in your e-smith server, I can recommend you to type them as follows:
domain.nl. IN MX 10 213.10.x.y.
domain.nl. IN MX 20 mailrelay.planet.nl.
Take care of the points after .nl and after the servername/ip address!
>Where do I have to put those lines?
What file/template?
If you have to put them in your e-smith's dns I really don't know, I'm sorry.