Update: 2023-05-03 00:25
Monitoring systems alerted that a large-scale DDoS attack directed to Cluster A of our Essential Email Service had been initiated on yesterday. Mitigation of the risks took place, however the unprecedented size of the attack exposed some limitations in the scalability of the authentication component of the service. The engineering team moved quickly to identify and address the root problem.
As of the time of this update, normal service operations have been restored, all users are now able to log in without issue, and all new send requests are being processed as expected. The remaining backlog of inbound email requests may take up to 12 hours to clear.
Having addressed the root issue, we are marking this incident as closed. We sincerely apologise for the impact this service interruption has had. In the coming weeks, an Incident Report will be released detailing the what happened, how it was approached and resolved, and how we will perform better in the future.