CLASS support

[jefsey]

At 18:32 30/11/2009, Kevin Darcy wrote:
>The default CLASS is "IN" (Internet). Unless you have a specific 
>need to use another class, then just leave CLASS empty and "IN" will 
>cover all of your typical name-resolution functions, e.g. 
>name->address, address->name, mail-domain->mail-exchangers, etc.

Dear Kevin,
I understand that. But I need to use Private Use classes. The 
question is how do I do it?
Best
jfc