A lot of systems block anything by default that isn't standard. For example, if you happen to own a domain to serve as your email that doesn't end in .com, .edu, .gov, then many systems will instantly invalidate you saying you don't have a valid email when in reality you do. A lot of companies or programmers don't seem to realize that its 2021 where we have hundreds of domain extensions to choose from.
I had a .ninja domain for a while, and I had to contact a certain DNS provide to add support for that TLD. They were very responsive, but I still had to ask.
