Changes / Mailgun / TLS Certificate Validation Errors for Clients Without SNI
Mailgun: Major incident: TLS Certificate Validation Errors for Clients Without SNI
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 from the diff below (Sol; type: incident outage). Check the diff before relying on it.
What changed
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After: TLS Certificate Validation Errors for Clients Without SNI
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After: major
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After: resolved
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After: 2026-04-15 13:40 UTC
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After: 2026-04-15 15:34 UTC
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After: API, Email Services - API
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After: 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.
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After: The issue has been identified and a fix is being implemented.
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After: A fix has been implemented and we are monitoring the results.
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After: This incident has been resolved.
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History of this incident
| When (UTC) | Change | Kind |
|---|---|---|
| Major incident: TLS Certificate Validation Errors for Clients Without SNI (this change) 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. | Major incident |