Resend email action

Send emails using a Resend hosted template. The template (layout, branding, subject) lives in the Resend dashboard; this action passes the template id and the variables, and Resend renders and sends the email.

It mirrors the template_id + dynamic_template_data model of the old SendGrid action, with one addition that works around a Resend limit (see Long values below).

Prerequisites

1. A verified sending domain in Resend (Settings → Domains).
2. A published template in Resend; note its id or alias.
3. A Resend API key stored as a secret in the consuming repository.

Inputs

Input	Required	Description
resend_api_key	yes	Your Resend API key.
to	yes	Recipient address(es), comma-separated. Max 50.
from	yes	Sender, e.g. Acme <noreply@your-verified-domain.com>.
template_id	yes	Resend template id or alias.
subject	no	Overrides the template's default subject when set.
dynamic_template_data	no	Newline-separated env var names → template variables (each ≤ 2000 chars).
chunked_template_data	no	Newline-separated env var names for large values (see below).
chunk_slots	no	Slots per chunked variable. Default 20 (~38k chars).
cc / bcc	no	Extra recipients, comma-separated.
reply_to	no	Reply-To address(es), comma-separated.

Like the SendGrid action, dynamic_template_data lists the names of environment variables; the value of each is read from the environment at run time. On success the action logs Email sent successfully. Id: <id>; on any failure it fails the step with a clear message — it never reports success for a send that did not go out.

Long values (the 2,000-char cap)

Resend caps every template variable value at 2,000 characters. Release notes routinely exceed that. Rather than truncate, list such variables under chunked_template_data: the action splits each value into chunk_slots pieces — release_notes_1, release_notes_2, … — each safely under the limit. Because the pieces are concatenated with no separator, your template reproduces the original value exactly:

{{{release_notes_1}}}{{{release_notes_2}}}{{{release_notes_3}}}{{{release_notes_4}}}{{{release_notes_5}}}{{{release_notes_6}}}{{{release_notes_7}}}{{{release_notes_8}}}{{{release_notes_9}}}{{{release_notes_10}}}{{{release_notes_11}}}{{{release_notes_12}}}{{{release_notes_13}}}{{{release_notes_14}}}{{{release_notes_15}}}{{{release_notes_16}}}{{{release_notes_17}}}{{{release_notes_18}}}{{{release_notes_19}}}{{{release_notes_20}}}

Notes:

• Use triple braces {{{ }}} so HTML in the value renders instead of being escaped.
• Keep the placeholders adjacent (no spaces/newlines between them) or the value won't reconstruct.
• The count must match chunk_slots (default 20). If a value needs more slots than available, the action fails with a clear message — raise chunk_slots and add matching placeholders.
• Empty trailing slots render to nothing, so short values are fine too.

Usage

- name: Send release email
  uses: liquidlab-agency/resend-action@master
  env:
    client_name: ${{ env.CLIENT_NAME }}
    release_version: ${{ inputs.tag_name }}
    release_notes: ${{ steps.html_convert.outputs.result }}   # full HTML, any length
  with:
    resend_api_key: ${{ secrets.RESEND_API_KEY }}
    from: 'LiquidLab <releases@your-verified-domain.com>'
    to: ${{ vars.RELEASE_RECIPIENTS }}
    template_id: ${{ vars.RESEND_RELEASE_EMAIL_TEMPLATE_ID }}
    dynamic_template_data: |
      client_name
      release_version
    chunked_template_data: |
      release_notes

Manual testing

A workflow_dispatch workflow (Manual Resend Test) is included. Add the RESEND_API_KEY secret, then run it from the Actions tab to send a real test email against a template id with values you type into the form.