Right now my site is sitting at media3.com hosts.
they are ok but they have a big problem- adservers like hotmail are blocking emails from their servers. that means that greeting cards that being sent through my site to hotmail and other companies never get to their destination.
I wrote my server and they moved my site to another server at their company but it still doesnt help.

I need some advices about other hosting companies with unlimited transfer, NT based.

Unlimited transfer? Im not going to touch that one.

There are 2 possible problems if your mail is not getting to one of the big boy IE aol or hotmail.

1. Make sure you have rnds set up on your domain, the big boys reject mail without a rdns resolve.

2. Your servers IP could be black listed do to spam.