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

- Impact (vendor’s label): major
- Status: resolved
- Started: 2026-02-24 19:07 UTC · Resolved: 2026-02-24 19:41 UTC · Duration: 34 min
- Updates: 6 · Affected components: Transmissions API - Transmissions API - USA, Transmissions API - USA
- [Vendor status page: https://stspg.io/vdhpx4p0k53n](https://stspg.io/vdhpx4p0k53n)
- [Company: SparkPost](https://rewindex.com/company/sparkpost.md)

## Timeline of updates

- **investigating** 2026-02-24 19:07 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.
- **investigating** 2026-02-24 19:07 UTC: We are continuing to investigate this issue.
- **investigating** 2026-02-24 19:25 UTC: We are continuing to investigate this issue.  We still see 5xx errors on mail injections and degradation.
- **identified** 2026-02-24 19:34 UTC: The team has identified the root cause.  There is a core networking issue that has impacted sending across the clusters.
- **monitoring** 2026-02-24 19:38 UTC: A fix has been implemented and we are monitoring the results.
- **resolved** 2026-02-24 19:41 UTC: This incident has been resolved.

## Rewindex changes for this incident

- 2026-02-24 19:07 UTC: [Major incident: Elevated 5xx Transmissions API error rates and latency for some SparkPost customers (US hosted only)](https://rewindex.com/change/i10bb3415f536f7.md)


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Canonical: https://rewindex.com/company/sparkpost/incidents/ndjn00g5vwm3 · Markdown: https://rewindex.com/company/sparkpost/incidents/ndjn00g5vwm3.md · JSON: https://rewindex.com/api/v1/companies/sparkpost/incidents/ndjn00g5vwm3 · Generated 2026-10-19T21:09:23.596Z