使用prometheus alertmanager通过Grafana UI发送警报电子邮件

我正在尝试使用prometheus alertmanager通知通道测试通过grafana UI发送电子邮件警报。我已经在alertmanager的配置文件中添加了stmp详细信息。当我尝试测试时，它说电子邮件已经发送，但什么都没有发生。当我将相同的电子邮件配置添加到grafana.ini文件并在UI中添加电子邮件通知通道时，我就可以发送测试通知了。我正在使用以下舵图进行安装->https://github.com/helm/charts/tree/master/stable/prometheus-operator这是alertmanager配置文件。

config:
global:
resolve_timeout: 5m
smtp_smarthost: 'email-smtp.us-east-1.amazonaws.com:587'
smtp_from: 'redacted'
smtp_auth_username: 'redacted'
smtp_auth_password: 'redacted'
route:
group_by: ['job']
group_wait: 30s
group_interval: 5m
repeat_interval: 12h
receiver: 'null'
routes:
- match:
alertname: DeadMansSwitch
receiver: 'null'
receivers:
- name: 'null'

这是格拉法纳日志。

t=2019-01-28T16:57:38+0000 lvl=info msg="Request Completed" logger=context userId=0 orgId=0 uname= method=GET path=/ status=302 remote_addr=127.0.0.1 time_ms=0 size=29 referer=
t=2019-01-28T16:59:07+0000 lvl=info msg="Request Completed" logger=context userId=1 orgId=1 uname=admin method=POST path=/api/alerts/test status=422 remote_addr=127.0.0.1 time_ms=36 size=82 referer="http://localhost:8000/d/6581e46e4e5c7ba40a07646395ef7b23/k8s-compute-resources-pod?refresh=10s&panelId=0&fullscreen&edit&orgId=1&tab=alert"
t=2019-01-28T16:59:56+0000 lvl=info msg="Request Completed" logger=context userId=1 orgId=1 uname=admin method=POST path=/api/alerts/test status=422 remote_addr=127.0.0.1 time_ms=37 size=82 referer="http://localhost:8000/d/a6e7d1362e1ddbb79db21d5bb40d7137/k8s-use-method-cluster?refresh=10s&panelId=0&fullscreen&edit&orgId=1&tab=alert"
t=2019-01-28T17:01:30+0000 lvl=info msg="Sending Alertmanager alert" logger=alerting.notifier.prometheus-alertmanager ruleId=0 notification=Alert
t=2019-01-28T17:02:30+0000 lvl=info msg="Sending Alertmanager alert" logger=alerting.notifier.prometheus-alertmanager ruleId=0 notification=Alert
t=2019-01-28T17:06:40+0000 lvl=info msg="Sending Alertmanager alert" logger=alerting.notifier.prometheus-alertmanager ruleId=0 notification=Alert

我在这里做错了什么？