Pre-install question about multiple domains

[brianhill1980]

I have a question regarding multiple domains and specifically email.

I had ispCP 1.0.0 installed on my web server and initially it worked perfectly. However I offered to host my brothers website and email using my web server. I set it all up, the virtual host was working with the correct domain name. The only problem I had was that when he tried sending emails from squirrelmail using his domain, it wouldn't work. But it would work fine for me using the domain the server was initially setup with.

I'd get a SMTP 111 error.

I'm re-installing Debian 5.0 and ispCP on my webserver, but I'm just wondering if there is anything special I need to do so that multiple domain names can be hosted from a single machine, and email works for all of them.

Thanks for any help!