Are you not using VPN or Tor browser, this has happened to me before when I tried to register on a site using Tor. If you are, remove it and try again
I wasn't using Tor or a VPN while trying to register honestly and I find it dumb even If I was because bitcoin users are known to be careful about their privacy .
It's not because of VPN or tor browser, I just tried now to sign up in purse.io with my outlook email and I wasn't unable, I got this message: "Certain Email providers are blocked. Please use Gmail or Yahoo." so seems that they have block outlook but they accept hotmail, I just tried it and with hotmail email it worked.
Yes that the exact issue I'm having , Outlook and hotmail are from the same provider so once again... this is definitely dumb from their part. thanks for the help , I will give it a try !