Early in the morning there was a DNS error which caused many clients to be unable to resolve our addresses. I was asleep at the time but the Akismet team fixed the error shortly after it was reported, but unfortunately due to the nature of DNS some clients appear to still be caching the “not found” errors, even 6‑7 hours after it’s been fixed.
This sucks, and any time there is a problem like this we have a thousand ideas about how to prevent anything like this from happening again. Over the next day or two we’ll be deciding Because of the nature of Akismet it hurts so much when there are any system problems, which is why we’ve been so fanatical about performance and reliabilit through several doublings of the volume of spam.
Now might be a good time to point out that we have a new version of the Akismet plugin for WordPress that adds a “Recheck queue” button to the moderation page. That way if something happens and you have a lot of comments stuck in moderation, with a single click Akismet can recheck them and clear out any known spam.