Starting late last night delivery to Hotmail/Windows Live Mail domains began to drop off. As of this morning it appears that barely one quarter of all mail bound for these domains is arriving at the inbox. According to our benchmark we are seeing almost 70% of all mail go missing. At the moment the exact reason for the delivery delays is undetermined.
ImplicationsHotmail servers seem to be refusing inbound connections. Mailers should anticipate seeing their mail queues build up; mail bound for hotmail should be retried as the problem appears to exist at the gateway of the ISP. We will continue to monitor delivery across all of our clients and will provide updates as more information becomes available.