这是alter manager配置默认需要证书，官方config解释：
参考链接：https://prometheus.io/docs/alerting/configuration/
The default SMTP TLS requirement.
Note that Go does not support unencrypted connections to remote SMTP endpoints.
[ smtp_require_tls: | default = true ]
所以设置 smtp_require_tls:False 即可。
AlterManagerConfigMap.yml: (我使用webhook,去掉routes:默认邮件发送)
level=error ts=2020-01-13T07:44:58.048Z caller=notify.go:372 component=dispatcher msg="Error on notify" err="Post <redacted>: x509: certificate signed by unknown authority" context_err="context deadline exceeded"
level=error ts=2020-01-13T07:44:58.048Z caller=dispatch.go:266 component=dispatcher msg="Notify for alerts failed" num_alerts=1 err="Post <redacted>: x509: certificate signed by unknown authority"
level=error ts=2020-01-13T07:44:58.548Z caller=notify.go:372 component=dispatcher msg="Error on notify" err="Post <redacted>: x509: certificate signed by unknown authority" context_err="context deadline exceeded"
level=error ts=2020-01-13T07:44:58.548Z caller=dispatch.go:266 component=dispatcher msg="Notify for alerts failed" num_alerts=1 err="Post <redacted>: x509: certificate signed by unknown authority"
level=error ts=2020-01-13T07:49:58.049Z caller=notify.go:372 component=dispatcher msg="Error on notify" err="Post <redacted>: x509: certificate signed by unknown authority" context_err="context deadline exceeded"
level=error ts=2020-01-13T07:49:58.049Z caller=dispatch.go:266 component=dispatcher msg="Notify for alerts failed" num_alerts=1 err="Post <redacted>: x509: certificate signed by unknown authority"
level=error ts=2020-01-13T07:49:58.549Z caller=notify.go:372 component=dispatcher msg="Error on notify" err="Post <redacted>: x509: certificate signed by unknown authority" context_err="context deadline exceeded"
level=error ts=2020-01-13T07:49:58.549Z caller=dispatch.go:266 component=dispatcher msg="Notify for alerts failed" num_alerts=1 err="Post <redacted>: x509: certificate signed by unknown authority"
level=error ts=2020-01-13T07:54:58.050Z caller=notify.go:372 component=dispatcher msg="Error on notify" err="Post <redacted>: x509: certificate signed by unknown authority" context_err="context deadline exceeded"
level=error ts=2020-01-13T07:54:58.050Z caller=dispatch.go:266 component=dispatcher msg="Notify for alerts failed" num_alerts=1 err="Post <redacted>: x509: certificate signed by unknown authority"
level=error ts=2020-01-13T07:54:58.549Z caller=notify.go:372 component=dispatcher msg="Error on notify" err="Post <redacted>: x509: certificate signed by unknown authority" context_err="context deadline exceeded"
level=error ts=2020-01-13T07:54:58.549Z caller=dispatch.go:266 component=dispatcher msg="Notify for alerts failed" num_alerts=1 err="Post <redacted>: x509: certificate signed by unknown authority"
