We're aware of an issue preventing the timely delivery of messages from external senders using Microsoft's Office 365 service. These delays are due to messages sent from this service being categorized as malicious by ProofPoint.
ProofPoint has resolved the issue but is still processing a large backlog of messages.
No action is required on the colleague's part, and messages that are stuck in the queue will likely be processed within the next 12 hours.
Please click here to contact the Help Desk if you have any additional questions or concerns.