Alertmanager fails to send SMTP notifications due to "starttls failed" errors regarding certificate signed by unknown authority

Solution Verified - Updated -

Issue

  • Alertmanager fails to send SMTP notifications for custom alerts.

  • The following errors stream in the alertmanager container logs:

    level=error ts=2019-09-05T20:41:09.059151352Z caller=notify.go:332 component=dispatcher msg="Error on notify" err="starttls failed: x509: certificate signed by unknown authority"
level=error ts=2019-09-05T20:41:09.059462294Z caller=dispatch.go:280 component=dispatcher msg="Notify for alerts failed" num_alerts=11 err="starttls failed: x509: certificate signed by unknown authority"

Environment

  • Red Hat OpenShift Container Platform
    • 4

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