(Resolved) Registration and notification emails going to spam
Fault: Emails for registration and notification were going straight to spam for users. Email clients (such as GMail) couldn't verify the legitimacy of the sender due to a mix-up in the DNS records preventing the clients verifying if the forum was indeed allowed to send from that domain.
Resolution: Updated the DNS records. Quick local test works while worldwide propagation of the fix can take up to 24 hours.