Elevated 5xx Transmissions API error rates and latency for some SparkPost customers (US hosted only)

Update timeline

1. investigating Feb 24, 2026, 07:07 PM UTC

   We are experiencing an elevated level of errors and latency on the Transmissions API (injection API) for some SparkPost customers. Please retry any 5xx error. Note: This issue does not impact SparkPost customers hosted in the EU.

2. investigating Feb 24, 2026, 07:07 PM UTC

   We are continuing to investigate this issue.

3. investigating Feb 24, 2026, 07:25 PM UTC

   We are continuing to investigate this issue. We still see 5xx errors on mail injections and degradation.

4. identified Feb 24, 2026, 07:34 PM UTC

   The team has identified the root cause. There is a core networking issue that has impacted sending across the clusters.

5. monitoring Feb 24, 2026, 07:38 PM UTC

   A fix has been implemented and we are monitoring the results.

6. resolved Feb 24, 2026, 07:41 PM UTC

   This incident has been resolved.