Folks, I think I may have just fixed what appears to have been a rather longstanding issue. Since early 2023, it looks like Google got stricter about anti-spam measures and started blocking our registration confirmation emails. From what I see (or rather, no longer see) in our logs, the problem appears to be solved after a small change on this end (update to SPF record.)

Apologies for taking so long to notice this. Dock this perv a day's pay for fappin' on the job!