If you receive the message: 

• We don't allow users with the email address provider you entered. Please try another email address.

During your signup at https://www.040support.nl it means your mail address or even mail domain are excluded from being allowed to sign up.

Because of the nature of webhosting criminals always try to sign up and abuse accounts for spam or other criminal intent, we try to avoid these issues, for our selfs but also for our clients, to do so, we limited some email providers due to the large amount of bad users coming from these domains,
think about sevices like maildrop.cc a free service to receive mail anonymously; same counts for many other 'free' mail providers where it is easy to create a temporary account for ill intent. (this does include hotmail, outlook, yahoo and alike).

We know that we may accidentally have locked you out as reader of this article, our apologie, we know that not everyone has a bad intention, this should not be a problem, your ISP in almost all cases provides you with a valid email address with your internet subscription, just use this for signing up and we are glad to welcome you at 040hosting.