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

**Summary:** _summary pending_
- Kind: Major incident · Label: major (vendor)
- Changed: 2026-02-24 19:07 UTC · Detected: 2026-10-19 18:53 UTC
- [Source: https://stspg.io/vdhpx4p0k53n](https://stspg.io/vdhpx4p0k53n)
- [Company: SparkPost](https://rewindex.com/company/sparkpost.md)
- Versions: before (none: first archived) → after incident\_version:755/ndjn00g5vwm3@648b5fc0acd2
- Change 1 of 1 for this incident

Incident page (full timeline): [Elevated 5xx Transmissions API error rates and latency for some SparkPost customers (US hosted only)](https://rewindex.com/company/sparkpost/incidents/ndjn00g5vwm3.md)
## What changed

**1. Added: Title**

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

**2. Added: Impact**

```diff
+ major
```

**3. Added: Status**

```diff
+ resolved
```

**4. Added: Start time**

```diff
+ 2026-02-24 19:07 UTC
```

**5. Added: Resolved time**

```diff
+ 2026-02-24 19:41 UTC
```

**6. Added: Affected components**

```diff
+ Transmissions API - Transmissions API - USA, Transmissions API - USA
```

**7. Added: Update** (investigating) · 2026-02-24 19:07 UTC

```diff
+ 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.
```

**8. Added: Update** (investigating) · 2026-02-24 19:07 UTC

```diff
+ We are continuing to investigate this issue.
```

**9. Added: Update** (investigating) · 2026-02-24 19:25 UTC

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

**10. Added: Update** (identified) · 2026-02-24 19:34 UTC

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

**11. Added: Update** (monitoring) · 2026-02-24 19:38 UTC

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

**12. Added: Update** (resolved) · 2026-02-24 19:41 UTC

```diff
+ This incident has been resolved.
```

## History of this incident

| When (UTC) | Change | Label |
| --- | --- | --- |
| 2026-02-24 19:07 UTC | Major incident: Elevated 5xx Transmissions API error rates and latency for some SparkPost customers (US hosted only) (this change) | major |

All SparkPost changes: [timeline](https://rewindex.com/company/sparkpost/changes.md)
_Diff excerpts are shown on normalized text: dates, counters and tokens appear as ‹date›, ‹count›, ‹tok›; noise-only edits are hidden. Rewindex shows the changed passages, not a copy of the page._


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Canonical: https://rewindex.com/change/i10bb3415f536f7 · Markdown: https://rewindex.com/change/i10bb3415f536f7.md · JSON: https://rewindex.com/api/v1/changes/i10bb3415f536f7 · Generated 2026-10-19T21:43:55.780Z