This is unrelated to the recent issues. The monthly limit for the email provider the site uses has been reached; seems there was a sudden spike yesterday / overnight. I'm not sure at this stage whether it's just a spike in genuine emails, something fishy, or (most likely) emails sent during the course of me working on the 2.1 upgrade on a local server.
I won't get a chance to investigate this until later today. In the meantime, keep an eye on your PMs and watched topics manually, and if anyone is trying to register and not able to verify, contact an admin via Discord or IRC and we can activate your account for you.
I've been still receiving emails about PM notifications throughout the day.
I do notice my account has 100% good standing, so maybe they're letting it slide due to that and/or noticing it's non-commercial use. Not really sure. At any rate it should reset in a few days, so between those two factors, I won't take any action for now.
It doesn't appear anything dodgy is going on, nor that testing contributed much to it (there's maybe 4 or 5 emails that would've been generated during testing / dev work on my local machine). A bit of a spike yesterday, but they're purely from PM notifications, to email addresses that I recognize as belonging to established users of the site. Just a busy month for site emails in general, it'd seem.