Can you find me a service/product which takes an input file of domain
names and returns an analysis of domain names and how important they
are.

For example, if I have a customer base of 10,000 emails and I strip
off the first part before @ from privacy and have file of things like
comcast.net, hotmail.com, ford.com, instantpundit.com, etc.

I want to find out the traffic estimate and rank (Alexa?) of the
domain, I want to know whether it is just a ISP domain and thus
nothing special, or whether it is a Fortune 1000 company, or if a
blog, and perhaps the whois info of owner, etc.

The goal is to try to find which customers are at Fortune 1000
companies, or are owners or involved with high traffic sites or blogs
for possible testimonials on the site or low-cost advertising.

Feel free to comment if this leads to more marketing ideas even if you
are not going to answer it.

Mr. SeekWisdomAlways...
I dont know of any tools that will do what you ask.... BUT there is a script
langauge out there called PERL which is perfectly suited for this type
application. PERL for Windows is available for free from
http://www.activestate.com  You just download the environment and
install it
and you can  then write Perl scripts. Perl is very powerful when working with
text type data. If your shop has experienced programmer, I'm sure he could
use Perl to manipulate the emails, extract the 'from' address, strip out the
user names and just keep the source domains. Then the program could be
written to do whatever you need. A good perl programming textbook is:
PERL (How to Program) by Harvey M. Deitel  (ISBN# 0-13-028418-1)
This book has many examples, excellent explanations, and loaded with
professional-grade tips and pointers.