Between October 31 14:00 UTC / 10:00 EDT and November 1 8:45 UTC / 4:45 EDT we have observed connection errors for some outgoing email which may have caused a delay in delivery. For emails submitted that are affected customers have received an automated notification (“Your message could not be delivered for more than 4 hour(s). It will be retried [...]“). Those queued emails are now being delivered again and do not need to be resubmitted.
The cause for this incident was a disconnected synchronization running on our firewalls which caused for some network paths to be denied traffic, resulting in connection timeouts. Restarting the synchronization resolved the issue.
We’re analyzing the problem to get to the root cause and to improve our monitoring. We sincerely apologize for any inconvenience caused by this glitch in our system and are actively working to prevent similar occurrences in the future. Thank you for your understanding.