dataiku · colincazabet · Jul 16, 2026 · Jul 10, 2026 · Jul 10, 2026 · Jul 15, 2026
diff --git a/custom-recipes/send-mails-from-contacts-dataset/recipe.json b/custom-recipes/send-mails-from-contacts-dataset/recipe.json
@@ -165,9 +165,10 @@
             "name": "html_body_value",
             "label" : "Body (HTML)",
             "type": "EMAIL_TEMPLATE_TEXTAREA",
-            "description" : "The body content supports JINJA templating. E.g. for a value from the input dataset use {{ column_name }}, for a table of attachment data {{ attachments.dataset_name.html_table }}, or to loop through an attachment dataset {% for row in attachments.dataset_name.data %}{{ row.column_name }}{% endfor %}",
+            "description" : "The body content supports JINJA templating. E.g. for a value from the input dataset use {{ column_name }}, for a table of attachment data {{ attachments.dataset_name.html_table }}, or to loop through an attachment dataset {% for row in attachments.dataset_name.data %}{{ row.column_name }}{% endfor %}. Preview renders with the first row of the contacts dataset only; runtime renders once per contacts row.",
             "defaultValue" : "<!-- Template with CSS starter kit -->\n<html><head><style type=\"text/css\"> * { font-family: Verdana, sans-serif; } table { width: 100%; border-collapse: collapse; border: 1px solid #ddd; } td { padding: 10px; text-align: left; border: 1px solid #ddd; } th { background-color: #f2f2f2; padding: 10px; text-align: left; border: 1px solid #ddd; }</style></head><body>\n{# add content underneath this - you can use JINJA templating, e.g. <b>{{ column_name }}</b> #}\n\n</body></html>",
-            "visibilityCondition" : "model.use_body_value && (model.body_format == 'html')"
+            "visibilityCondition" : "model.use_body_value && (model.body_format == 'html')",
+            "templatePreviewCallback": "preview_email_body"
         },
         {
             "name": "use_body_value",

diff --git a/resource/dynamic_form.py b/resource/dynamic_form.py
@@ -1,7 +1,65 @@
 from dss_selector_choices import DSSSelectorChoices, SENDER_SUFFIX
 from dku_support_detection import supports_messaging_channels_and_conditional_formatting
+from jinja2 import Environment, StrictUndefined
+from dku_attachment_handling import attachments_template_dict
+from email_utils import build_email_message_text
 import dataiku
 
+EMAIL_TEMPLATE_PREVIEW_CALLBACK = "preview_email_body"
+
+jinja_env = Environment(undefined=StrictUndefined)
+
+
+def _input_names_for_role(inputs, role):
+    return [
+        input_desc.get("fullName")
+        for input_desc in (inputs or [])
+        if input_desc.get("role") == role and input_desc.get("fullName")
+    ]
+
+
+def _first_row(dataset):
+    for row in dataset.iter_rows():
+        return dict(row)
+    return None
+
+
+def preview_email_body(payload, config, inputs):
+    html = config.get(payload["parameterName"], payload["html"])
+
+    contact_names = _input_names_for_role(inputs, "contacts")
+    if not contact_names:
+        return {"html": html}
+
+    people = dataiku.Dataset(contact_names[0])
+    contact_dict = _first_row(people)
+    if contact_dict is None:
+        return {"html": html}
+
+    attachment_datasets = [
+        dataiku.Dataset(dataset_name)
+        for dataset_name in _input_names_for_role(inputs, "attachments")
+    ]
+
+    try:
+        attachments_templating_dict = attachments_template_dict(
+            attachment_datasets,
+            dataiku.default_project_key(),
+            (config or {}).get("apply_coloring_excel", False),
+        )
+        body_template = jinja_env.from_string(html)
+        rendered_html = build_email_message_text(
+            True,
+            body_template,
+            attachments_templating_dict,
+            contact_dict,
+            None,
+            True,
+        )
+    except Exception as e:
+        return {"error": str(e)}
+
+    return {"html": rendered_html}
 
 def do(payload, config, plugin_config, inputs):
     dss_client = dataiku.api_client()
@@ -22,11 +80,16 @@ def do(payload, config, plugin_config, inputs):
             else:
                 choices.append(f"{channel.id}", channel.id)
 
-        # Add an entry for direct SMTP
+                # Add an entry for direct SMTP
         if len(channels) > 0:
             # If there is a choice of channels, giving direct SMTP a key of "__DKU__DIRECT_SMTP__" means it is there but not as default
             choices.append("Manually define SMTP", "__DKU__DIRECT_SMTP__")
         else:
             # If there is no choice, put SMTP there but with a key of None, so it will be the default instead of "Nothing selected"
             choices.append("Manually define SMTP", None)
         return choices.to_dss()
+
+    if payload.get("templatePreviewCallback") == EMAIL_TEMPLATE_PREVIEW_CALLBACK:
+        return preview_email_body(payload, config, inputs)
+
+    return {}