Customers got an email from Circle immediately after they were able to "resolve" the issue. The full post-mortem was released recently. We got the email on Jan 4 or Jan 5.
Some customers got such an email, but not all of them (also see https://news.ycombinator.com/item?id=34255721). The only email received by people in my org was the email pointing to the post-mortem, which went out on 2022-01-13.
