Mailgun: TLS Certificate Validation Errors for Clients Without SNI

Impact: majorStatus: resolvedStarted 2026-04-15 13:40 UTCResolved 2026-04-15 15:34 UTC (1.9 h)4 updatesSource: stspg.io

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 archived incident (Sol). Check the timeline before relying on it.

Affected components: APIEmail Services - API

Timeline of updates

investigating2026-04-15 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.
identified2026-04-15 13:42 UTC
The issue has been identified and a fix is being implemented.
monitoring2026-04-15 14:02 UTC
A fix has been implemented and we are monitoring the results.
resolved2026-04-15 15:34 UTC
This incident has been resolved.

Rewindex changes for this incident

Major incident: TLS Certificate Validation Errors for Clients Without SNI 2026-04-15 13:40 UTC

Impact, status and times are the vendor’s own, as last archived. View on stspg.io (opens in new tab). Mailgun profile · Recent Mailgun incidents · Markdown · JSON