There seems to have been an issue with the server being unable to send e-mails, and thus everyone trying to register was unable to so during the last 12 days.
I was only made aware of the issue yesterday, and it seems I was able to fix it...
I had SMF re-send activation e-mails for users that tried to register in the past 12 days, and it looks successful because just now one of those users posted. \o/
Sorry for the inconvenience.
Turns out I hadn't exactly fixed the problem. If I did, it was only partially.
Microsoft thought wise of blacklisting us, while no one else has (see yourself (http://mxtoolbox.com/SuperTool.aspx?action=blacklist%3affhacktics.com&run=toolpage)). I'm rather pissed at them, because I bet it's because our domain name has the word "hack" in it; oh noes. This is a dedicated server, so I don't see how someone could've used it to spam e-mails.
Basically this prevented the server from sending any email to hotmail/msn/live/outlook/etc.
One option not so available was convincing M$ to take us off from the blacklist... An apparently extremely tedious process, and they're assholes about too.
In any case, I have finally fixed the problem by configuring the forum to use gmail's SMTP, but sadly I reached the daily limit of ~150 emails that I can send per day. So if you receive any PM today or anything, you won't get any e-mail notification. Likewise, it won't be possible to start and complete registering today. Said e-mails will be queued and delivered tomorrow. I can always provide some assistance if you join IRC.
I apologize for the inconvenience. Blame M$.
Well, for anyone that cares, everything should be back in order. Everyone with an account that didn't receive an activation e-mail now should.