If you mean 'applying' to join the forum, all @gmail.com, @hotmail.com, and other email domains are blocked. This is to stop 'forum spammers' from joining the forum.
You will notice that there are very few members, but I get at least 10 attempts to join the forum from @gmail.com email addresses per day.
There are some anti-Spam modules available for the forum software, but I have not installed these.
Ian