Alerts get stuck with an empty inbox

Support
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1

NethServer Version: 8
Module: Settings + Grafana

I have email notifications enabled.
Due to a rule in my firewall, the Let’s Encrypt certificate hasn’t been renewed and will expire on September 30.
Today I started receiving alerts (Grafana? NS8?), but I’m having these issues:

  1. The email arrives empty: no subject line, no message body, just mail headers.
  2. The message arrives every 5 minutes, and I can’t find a way to disable it

I logged into Grafana and saw an “Alert Rule” for “TLS certificates” with a red label that says “1 firing”; it’s

X-Mozilla-Status: 0001
X-Mozilla-Status2: 00000000
Return-Path: <ns8***@*****>
Received: from em.*****
	by em.***** with LMTP id OCSHMMr4s2oZGwAAoNHYhA
	; Wed, 23 Sep 2026 09:05:30 -0700
Received: from ***** (gateway [10.0.1.1])
	(Authenticated sender: ***@*****)
	by em.***** (Postfix) with ESMTPSA id C57CCE4865
	for <*****@*****>; Wed, 23 Sep 2026 09:05:30 -0700 (MST)
Authentication-Results:em.*****; dkim=permerror (bad message/signature format)
X-Spamd-Result: default: False [0.00 / 20.00];

2026-09-23_01_emtpy_mails
2026-09-23_01_emtpy_mails1355×360 45.6 KB

2026-09-23_04_grafana_alert_rules
2026-09-23_04_grafana_alert_rules1483×677 71.9 KB

2026-09-23_03_grafana_alerting
2026-09-23_03_grafana_alerting1483×460 54.3 KB

Thanks in advance. Regards

Edit 1: Is there a way to force the certificate update without breaking anything?

2

Traefik renews the certificate automatically. Make sure the Let’s Encrypt requirements for the HTTP challenge are met: TLS certificates | NethServer 8 documentation

A renewal attempt runs once per day. Once the firewall rule no longer blocks the challenge, wait until the next day and check whether the renewal succeeded.

From the Grafana screenshot I can see the alert details are present, so the empty subject and body probably come from a custom mail template. You may have copied and pasted a command that changed the mail_template attribute, as described in GitHub - NethServer/ns8-metrics: NS8 metrics and alerts · GitHub. Setting mail_template back to an empty string restores the default template.

3

Thanks, @davidep

As for Grafana, I haven’t edited any templates (except that yesterday, after writing the post, I assigned the default template in the hope that it would display something), but other than that, nothing has been changed. This is the first time I’ve been able to log into Grafana after several attempts since I installed this server a few months ago.

This is the only change after my original post:

image
image1030×782 81 KB

There is a way to “pause” the Alter or to have it fire only once a day.?

image
image1401×176 15.6 KB

4

Grafana does not send alerts in NS8. The relevant component is Prometheus Alert Manager and you may have configured with an api-cli run to use a non-existing (hence empty Subject) message template. In this case, follow the ns8-metrics README to fix it.

For example:

api-cli run module/metrics1/configure-module --data '{"prometheus_path": "", "grafana_path": "grafana", "mail_to": ["alert@example.org"], "mail_from": "no-reply@example.org", "mail_template": ""}'
5

Thanks @davidep :trophy:

This fixed the flood of messages.

Best regards.