Prometheus : Set Alert Notification (Email)2026/03/26

This is the Alert Notification Settings on Prometheus.

There are many way to receive Alerts like Slack, HipChat, WeChat and others, though, on this example, Configure Alerting with Email Receiver.

For more details of Alerting, Refer to the official documents.
⇒ https://prometheus.io/docs/alerting/configuration/

[1]

For Email notification, it needs SMTP Server.
On this example, it based on the environment that SMTP Server is running on localhost.

[2]

Install Alertmanager on Prometheus Server Host.

# install from EPEL

[root@dlp ~]#

dnf --enablerepo=epel -y install alertmanager

[3]	Configure Prometheus Alert Settings with Email notification.

[root@dlp ~]#

mv /etc/prometheus/alertmanager.yml /etc/prometheus/alertmanager.yml.org

[root@dlp ~]#

vi /etc/prometheus/alertmanager.yml

# create new

global:
  # SMTP server to use
  smtp_smarthost: 'localhost:25'
  # require TLS or not
  smtp_require_tls: false
  # notification sender's Email address
  smtp_from: 'Alertmanager <root@dlp.srv.world>'
  # if set SMTP Auth on SMTP server, set below, too
  # smtp_auth_username: 'alertmanager'
  # smtp_auth_password: 'password'

route:
  # Receiver name for notification
  receiver: 'email-notice'
  # grouping definition
  group_by: ['alertname', 'Service', 'Stage', 'Role']
  group_wait:      30s
  group_interval:  5m
  repeat_interval: 4h

receivers:
# any name of Receiver
- name: 'email-notice'
  email_configs:
  # destination Email address
  - to: "root@localhost"

# configure Alerting rules

[root@dlp ~]#

vi /etc/prometheus/alert_rules.yml

# create new
# for example, monitor node-exporter's [Up/Down]

groups:
- name: Instances
  rules:
  - alert: InstanceDown
    expr: up == 0
    for: 5m
    labels:
      severity: critical
    annotations:
      description: '{{ $labels.instance }} of job {{ $labels.job }} has been down for more than 5 minutes.'
      summary: 'Instance {{ $labels.instance }} down'

[root@dlp ~]#

vi /etc/prometheus/prometheus.yml

# Alertmanager configuration
alerting:
  alertmanagers:
  - static_configs:
    - targets: ['localhost:9093']

# line 23 : add alert rules created above
rule_files:
  # - "first_rules.yml"
  # - "second_rules.yml"
  - "alert_rules.yml"

[root@dlp ~]#

systemctl restart prometheus prometheus-alertmanager

[root@dlp ~]#

systemctl enable prometheus-alertmanager

[4]	If [node-exporter] is down, following Email is sent.

[root@dlp ~]#

mail

[-- Message  2 -- 229 lines, 10576 bytes --]:
Subject: [FIRING:1] InstanceDown (node01.srv.world:9100 Hiroshima example critical)
To: root@localhost
From: Alertmanager <root@dlp.srv.world>
Message-Id: <1774486634036009827.7672564156810088800@dlp.srv.world>
Date: Thu, 26 Mar 2026 09:57:14 +0900


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