We've been notified that the issue is resolved and all delayed mail has now been sent.
Posted Feb 20, 2020 - 03:55 UTC
Update from Sendgrid: "We have confirmed the subset of delayed mail has fully dequeued. We’re currently monitoring system performance. We apologize for any inconvenience this may have caused. Please contact our Support team at https://support.sendgrid.com with any questions."
Posted Feb 20, 2020 - 02:44 UTC
Update from Sendgrid: "We've confirmed that new mail received is being processed and delivery is attempted as normal. We are currently working to dequeue the subset of mail that was delayed between approximately 4:30 pm MT and 5:00 pm MT. We will continue to update as that mail dequeues."