Email Action

The email action delivers messages to email subscribers based on window status events.

Notifications can be triggered when the window changes its status as well as periodically while its status is REPEAT.

Email Client

Messages generated by the rule engine are sent by the built-in Mail Client which is configurable on the Settings > Mail Client page.

Custom Mail Client formatting options such as header and footer are applied to all outgoing messages.

Enable Notifications

Open the Email Notifications tab in the rule editor.

Set status to Enabled and enter one or multiple email addresses, separated by comma, semi-colon or whitespace.

Click 'Enabled' to subscribe to notifications initiated by OPEN, REPEAT, and CANCEL triggers.

For the REPEAT status, adjust the 'Repeat Interval' to the desired notification frequency, for example, every 6 hours or every 10 events.

If necessary, uncheck the Same as 'On Open' setting to adjust message content based on window status.


Name Description
Enabled Enable or disable email delivery.
Name User-defined email configuration name. Each rule can have multiple configurations which are executed independently.
Recipients One or multiple email subscribers to receive messages. Use a comma, semi-colon or whitespace to separate multiple addresses.
Priority Message priority to classify messages in commonly used email clients: Low, Normal, High.
Merge Messages Merge multiple notifications from different rules into one email message for the same subscriber to prevent too many emails arriving within a short time span. The Subject of merged messages is generated automatically and contains rule names, metric names, and the total number of merged notifications in the given message. For example: Alerts(2)-cpu_busy: statistical-time, nmon_cpu.
Minimum Notification Interval Minimum interval between messages to prevent too many email messages generated by the rule. The rule engine discards messages that are generated by the rule before the specified interval from the last sent message expires.

Configure Message Content

Fill out the message 'Subject' and 'Text' fields.

Both fields may include any text as well as placeholders to customize outgoing messages based on alert details.

Warning! Rule ${rule} for server ${entity} is active.

The placeholders, escaped with $ and wrapped in curly brackets such as ${expression}, are evaluated and replaced with actual values when the notification is sent.

Warning! Rule JVM Memory Low for server nurswgvml007 is active.

Subject Field

The 'Subject' field may include plain text, HTML entity characters, and emoji. HTML markup is not supported.

Note that long subjects that exceed the 78 characters according to RFC 2822, Section 2.1.1 may be truncated or rejected by mail servers. The actual limit is typically higher but is implementation-specific.

If placeholders in the subject can potentially evaluate to long strings, apply truncate or abbreviate functions to ensure that the subject length remains within the limit.

${entity} received message '${abbreviate(tags.notification, 50)}'

Text Field

The 'Text' field may include any text including emoji and HTML entity characters as well as placeholders.

Unlike the 'Subject' field, 'Text' is not constrained by a length limit and supports HTML markup.

Database Error.
Code: <b>${tags.code}</b>

The message text can include output of scripts, SQL queries, and API calls formatted as HTML tables.

Top-10 running containers by CPU:
${addTable(executeSqlQuery(query), 'html', true)}

In addition, the 'Text' field may invoke attachment functions to include portal screenshots as inline images or CSV files as attachments.

${addPortal('AWS Route53 Health Check Detail', aws_entity)}

The 'Text' field supports control flow syntax which allows customizing the content based on alert details.

@if{tags.payload.type != 'cron'}

Trigger Settings

Setting Description
Delay on Open Delay interval for sending notification for OPEN status. If the window changes to CANCEL status within the specified delay interval, no OPEN status email is sent. Set this interval to prevent emails on short-lived spikes.
Repeat Interval Interval for sending REPEAT status notifications. If the Repeat Interval is set in time units, the exact interval may vary because the REPEAT notifications are triggered by incoming data. In particular, REPEAT notifications are not sent if the data stops flowing in.
Subject Custom subject text, specified for each status separately. The subject can include placeholders with built-in fields, functions, and expressions, for example: ${round(avg())}. Note that the maximum allowed length of the subject is limited to several hundred characters in most email clients.
Text Custom message text, specified for each status separately. The text can include placeholders with built-in fields, functions, and expressions, for example: ${round(avg())}.
Attach Details Include a summary table with window statistics and action links.
Attach Portals One or more portal screenshots attached to the message as inline images. If a portal is a template, placeholders such as entity, metric, tags are resolved from the window fields.
Series Chart - attach a screenshot containing series monitored by this rule.


The incoming data is grouped into windows by metric, entity, and command tags with each window generating emails separately from the others.

If the rule creates too many windows, restrict the rule filter or add Override exceptions that disable alerting for a particular series.

The override table below contains rules that always return false for the matching series since the value cannot exceed 100%.

Message Composition

  • Subject
  • Content
    • Header
    • Text
    • Detail Table
      • Entity tags
      • Alert fields
      • Command/Event tags
      • User variables
    • Portal Screenshots (inline images in png format)
    • Footer
    • Attachments
      • Files (CSV, Excel, PDF, etc)


The subject may include placeholders with expressions substituted with actual values when the message is sent. If the placeholder is not found, the placeholder is replaced with an empty string.

Sample subject:

  [${status}] Rule ${rule} for ${entity} ${tags}

When using placeholders that may be replaced with text of arbitrary length, apply the truncate or abbreviate functions to limit the subject length.

  [${status}] Rule ${rule} for ${entity}: ${truncate(tags.error, 100)}


The message text (body) may include placeholders as well.

Use the HTML tag <br> to split content into multiple lines.

  Start Time: ${windowStartTime}<br>
  Duration: ${(timestamp / 1000 - windowStartTime) * 1000} ms

Placeholders with link fields are automatically inlined.

The message text can include control flow statements for conditional processing.

[${upper(tags.status)}] ${entityLink} Ω ${getEntityLink(tags.docker-host)}
<span style='color: orange'>${marker}</span>
  ${addTable(entity.tags, 'html')}

A header and footer can be specified in both plain text and HTML format in the Email Client settings and applied to all messages.

The header and footer do not support any placeholders.

<p style="color: #8db600; font-weight: bold; margin: 0px; padding: 0px;">Classification: UNCLASSIFIED</p>
<p style="color: #8db600;">END of MESSAGE</p>

Details Table

The details table is optional and is formatted with styles for enhanced readability in commonly used email client software.

The table includes multiple parts which are compiled depending on the alert context.

At the end of the table, the links are provided to view extended alert information, open charts and export underlying data.

Decimal numbers are rounded to 5 significant digits for readability.


To attach screenshots, a web driver must be installed and configured. To attach default portal for the current metric, entity and tags to the outgoing message, check the Series Chart option.

The chart may include multiple series depending on statistical functions referenced in the condition.

  abs(forecast_deviation(median())) > 2 && (median() < 200 || median() > 600)

Similarly, if the rule correlates multiple metrics using database functions or rules functions such metrics may be included in the screenshot on the right axis.

  avg() > 10 && db_last('memfree') < 500000

To attach additional portals, select them from the Additional Portal drop-down.

If a portal is a template, placeholders such as entity, metric, tags are set based on the current window fields.


The number of messages sent per minute can be monitored with the email_notifications_per_minute metric collected by ATSD.