invalid e-mail address

when I go to a web site to register and they asked for an e-mail and it makes no matter what email address I use, yahoo, aol, hot mail. any it tells me that that's it invalid. I've done everything to fix this and asked and no one can tell me how to?

Thanks.

many sites don't like hotmail and yahoo, few have blocked registrations from gmail though. They're just trying to weed out trash registrations on the site.

one that I was having a problem with was. freecreditreport.com so I used my phone internet and I could register there and then could come back to me computer and sign in and it was an aol e-mail address. ;\