Using the Send Email Action in Knack Flows

What You'll Learn

This article covers the Send Email action in Knack Flows: what it does, how to configure it, and when to use it instead of Email Actions or Email Rules in the Knack Builder.

What the Send Email Action Does

Send Email is one of Knack's own actions available inside Flows. It sits alongside Create Record, Update Record, Search for a Single Record, Search for Multiple Records, Search for Record ID, and Delete Record in the action list for the Knack connector. Add it as a Step in any Flow to send an email whenever that Step runs.

Because it lives in Flows rather than on a page element, the Send Email action doesn't need a form submission to fire. Any Trigger, a Knack record event, a schedule, a webhook, or an event from another Linked App, can lead into a Send Email Step.

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Send Email action vs. Email Actions and Email Rules
The Send Email action in Flows is a separate tool from Email Actions configured on a form element and from Email Rules configured in the Builder. Email Actions and Email Rules only fire when a Knack form element is submitted in the Live App. The Send Email action fires whenever its Step in the Flow runs, whether or not a Knack form was involved.

When to Use the Send Email Action

Pair it with a Record Created or Record Updated Trigger on a table to send a notification whenever a record changes, even if that record never passed through a Knack form.
Add it after a scheduled or webhook Trigger to send a reminder, report, or status update.
Combine it with the Router tool to send different emails down different branches of a Flow based on conditions.
Use it in custom frontend builds where records are created through the Runtime Data API instead of a Knack form. See the custom frontend section below for why this matters.

Setting Up the Send Email Action

Add the Action to Your Flow

Builder > Flows > Automations > [open or create a flow] > Add action

In the Add An Action modal, choose Knack as the app to transfer data to.
Open the Choose an action you want to perform dropdown. Send Email appears with Create Record, Update Record, Search for a Single Record, Search for Multiple Records, Search for Record ID, and Delete Record.
Select Send Email.
Choose your Knack app under Connect your Knack app.
Click Continue.

Configure the Required Fields

Continuing opens the Knack: Send Email configuration screen. Two fields are required:

Subject, the email's subject line.
Message, the body of the email.

Both fields accept typed text, a value pulled from an earlier Step in the Flow, or a mix of both.

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Confirm before publishing
It isn't confirmed whether Message supports HTML or rich formatting, or plain text only. The field in the Builder looks like a plain text input, unlike the WYSIWYG editor used for Email Actions on a form. Verify before this section goes live.

Configure the Recipient Fields

Three optional fields are visible by default:

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Confirm before publishing
It isn't confirmed what happens if To is left blank, whether the Step errors, sends to no one, or falls back to a default address. Verify and document the actual behavior before publishing this section.

Expand the Additional Fields

Click Show all fields to reveal three more optional fields:

Reply To
From
From name

Click Collapse to hide them again.

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No attachment field
The expanded field list doesn't include an attachment option. Confirm whether attachments are supported anywhere in this action before telling customers they aren't.

Save the Action

Click Save to add the Step to your Flow.

Example: Emailing a Patient When a Record Is Created

This example sends an email every time a new record is added to a Patients table, without requiring that record to come from a Knack form.

Create a new automation and open the flow builder.
Click Add trigger. In the Set Up A Trigger modal, choose Knack as the app, choose Record Created as the event, connect your Knack app, and select the Patients table under Tables.
Click Continue. The canvas now shows the Record Created Step with an Add action Step below it.
Click Add action and follow the steps above to add a Send Email action connected to the same Knack app.
In Subject and Message, type your text and insert values from the Record Created Step where you want patient-specific details, like the patient's name, to appear in the email.
Fill in To with the recipient, either a static address or a value from the triggering record.
Save the action, then click Start to turn the automation on.

Using the Send Email Action with a Custom Frontend

Email Actions on a form element and Email Rules in the Builder only fire when someone submits a Knack form element in the Live App. If your frontend writes records directly through the Runtime Data API, those Knack-side rules never see the write, so they never fire.

The Send Email action gives you a Flows-side equivalent. Pair it with a Record Created or Record Updated Trigger on the relevant table, and the email fires on the data event itself rather than on a form submission, regardless of whether the record came from a Knack form, the API, or another Linked App.

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Your frontend platform may already send some emails on its own
Some custom frontend platforms include their own email sending for specific cases, often gated by plan or by who the recipient is. The Send Email action in Flows isn’t tied to any one event. It fires on whatever Trigger you build it from, a record change, a schedule, a webhook, so it covers cases a platform’s built-in email feature might not.

Common Mistakes

Expecting it to behave like Email Actions in the Builder. Email Actions and Email Rules only fire from a Knack form submission. If your frontend writes through the API, use a Record Created or Record Updated Trigger with a Send Email action instead.
Leaving Subject or Message blank. Both are required. The action won't save without them.
Mapping a value that doesn't exist yet in the Flow. You can only insert values from Steps that run earlier in the same Flow, not from Steps that come after the Send Email action.

Next Steps

Knack Connectors: see every trigger and action Knack itself provides inside Flows, including Send Email.
Flows: Action Setup: general guidance on adding and ordering Actions in a Flow.
Flows: Trigger Conditions: control exactly when a Trigger, like Record Created, fires.