# Mailgun: TLS Certificate Validation Errors for Clients Without SNI

- Impact (vendor’s label): major
- Status: resolved
- Started: 2026-04-15 13:40 UTC · Resolved: 2026-04-15 15:34 UTC · Duration: 1.9 h
- Updates: 4 · Affected components: API, Email Services - API
- [Vendor status page: https://stspg.io/xc1w9hchy2bd](https://stspg.io/xc1w9hchy2bd)
- [Company: Mailgun](https://rewindex.com/company/mailgun.md)

## Summary

Mailgun reported a major API incident: HTTPS clients without Server Name Indication (SNI) received an expired SSL/TLS certificate, causing certificate validation failures. It started at 2026-04-15 13:40 UTC and was resolved at 2026-04-15 15:34 UTC, lasting 1 h 54 min; a fix was implemented at 04-15 14:02 UTC. _(machine-written, sol)_
## Timeline of updates

- **investigating** 2026-04-15 13:40 UTC: We are currently investigating an issue where customers making HTTPS requests to our API without Server Name Indication (SNI) enabled are being presented with an expired SSL/TLS certificate. This results in certificate validation failures for affected clients.
- **identified** 2026-04-15 13:42 UTC: The issue has been identified and a fix is being implemented.
- **monitoring** 2026-04-15 14:02 UTC: A fix has been implemented and we are monitoring the results.
- **resolved** 2026-04-15 15:34 UTC: This incident has been resolved.

## Rewindex changes for this incident

- 2026-04-15 13:40 UTC: [Major incident: TLS Certificate Validation Errors for Clients Without SNI](https://rewindex.com/change/i14e0c0646cb538.md)


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Canonical: https://rewindex.com/company/mailgun/incidents/wdl07xh4b6j7 · Markdown: https://rewindex.com/company/mailgun/incidents/wdl07xh4b6j7.md · JSON: https://rewindex.com/api/v1/companies/mailgun/incidents/wdl07xh4b6j7 · Generated 2026-10-18T11:44:46.924Z