Customers injecting mail in the US region via the SMTP API (smtp.sparkpostmail.com) experienced delivery delays yesterday of up to 30 minutes for some messages between 2020-05-26 17:56 and 19:10 UTC. Customers using the REST API or a different SMTP API endpoint were not impacted. During the incident, the customer impact was not fully understood and we did not issue a Status Page alert. The issue is now fully resolved and we are focused on understanding the root cause and mitigation plan. If you have further questions please contact Support or your Technical Account Manager. We sincerely apologize for not alerting you yesterday. Thank you for your patience.