Mailgun change history: TLS Certificate Validation Errors for Clients Without SNI

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.