RESOLVED: Throttling introducing delivery delays to O365 Exchange Online

It appears the Office 365 Exchange Online is throttling SMTP connections from our cloud-hosted Cisco CES antispam appliances. This is resulting in delays in the delivery of some inbound messages. Internal message delivery is not impacted, nor is outbound mailflow. An case is being opened with Microsoft support to rectify this.

Latest Update: 2019-01-12 06:02:26 - All delivery queues have successfully drained and the affected appliances have been returned to service.