[thelist] multiple domains SEO

[Andrew]

I have just been requested to order many domains that will all be associated
with one main domain.

The question is do I sub mask them all to the main domain or do I create
individual index pages that will point to the main domain name?

My concern will be search engines not liking this practice?  Will the main
domain be less thought of for having 20 domains poiting to it?  Or submasked to
it?

Cheers
Andrew