Have encountered the same problem multiple times. (on mk7)
People contact me on Miiverse because they can't join the pp.
Most of them do have a forum account by now. After trying multiple times. Maybe some are so young that they aren't used to or don't know how to make a forum account. And probably some got the math question wrong.
But there are people I know who do everything right and don't receive a confirmation email. After 5 or maybe 10 times trying, they receive one.
Some receive it in the spam inbox too, of course.
But I agree there is a problem that there are players that want to join but never do because of this  

Bastien and me tried it ourselves by making a new account. But it worked fine, for us.

Darren wrote on 10/12/15 at 05:34:09:


Me too me it looked but if you're looking at gmail.com "spam " folder and you will see the message is in there.

Darren wrote on 10/12/15 at 14:21:56:


They should try registering with a gmail account.

He said he'd try Gmail but hasn't got back to me yet

It could be that hotmail (or some other email service) is blocking or rejecting messages from the forum host's mail IP address.  It might be possible for an admin of the forum software to specify an alternative outgoing mail server through the admin interface.