Dynamic email registration recipients using variables

src/openforms/js/compiled-lang/en.json

@@ -5457,6 +5457,12 @@
       "value": "the variable"
     }
   ],
+  "mOh/pF": [
+    {
+      "type": 0,
+      "value": "The email address described in this variable will be used for the mailing. If a variable is selected, the general registration addresses will be used as fallback option."
+    }
+  ],
   "mOjKcm": [
     {
       "type": 0,
@@ -6273,6 +6279,12 @@
       "value": "Do not display the configured label and top line as the header in the fieldset."
     }
   ],
+  "uwCD8e": [
+    {
+      "type": 0,
+      "value": "Using a variable to decide to which email address the submission details will be sent"
+    }
+  ],
   "vAZDY4": [
     {
       "type": 0,

src/openforms/js/compiled-lang/nl.json

@@ -5475,6 +5475,12 @@
       "value": "de variabele"
     }
   ],
+  "mOh/pF": [
+    {
+      "type": 0,
+      "value": "The email address described in this variable will be used for the mailing. If a variable is selected, the general registration addresses will be used as fallback option."
+    }
+  ],
   "mOjKcm": [
     {
       "type": 0,
@@ -6291,6 +6297,12 @@
       "value": "Verberg de koptekst en de lijn boven de veldengroep in het formulier."
     }
   ],
+  "uwCD8e": [
+    {
+      "type": 0,
+      "value": "Using a variable to decide to which email address the submission details will be sent"
+    }
+  ],
   "vAZDY4": [
     {
       "type": 0,

src/openforms/js/components/admin/form_design/registrations/email/EmailOptionsForm.js

@@ -51,6 +51,7 @@ EmailOptionsForm.propTypes = {
     emailSubject: PropTypes.string,
     paymentEmails: PropTypes.arrayOf(PropTypes.string),
     toEmails: PropTypes.arrayOf(PropTypes.string),
+    toEmailsFromVariable: PropTypes.string,
   }),
   onChange: PropTypes.func.isRequired,
 };

src/openforms/js/components/admin/form_design/registrations/email/EmailOptionsFormFields.js

@@ -17,6 +17,7 @@ import EmailHasAttachmentSelect from './fields/EmailHasAttachmentSelect';
 import EmailPaymentSubject from './fields/EmailPaymentSubject';
 import EmailPaymentUpdateRecipients from './fields/EmailPaymentUpdateRecipients';
 import EmailRecipients from './fields/EmailRecipients';
+import EmailRecipientsFromVariable from './fields/EmailRecipientsFromVariable';
 import EmailSubject from './fields/EmailSubject';
 
 const EmailOptionsFormFields = ({name, schema}) => {
@@ -37,6 +38,7 @@ const EmailOptionsFormFields = ({name, schema}) => {
     <ValidationErrorsProvider errors={relevantErrors}>
       <Fieldset>
         <EmailRecipients />
+        <EmailRecipientsFromVariable />
         <EmailSubject />
         <EmailContentTemplateHTML />
         <EmailContentTemplateText />

src/openforms/js/components/admin/form_design/registrations/email/fields/EmailRecipientsFromVariable.js

@@ -0,0 +1,46 @@
+import {useField} from 'formik';
+import React from 'react';
+import {FormattedMessage} from 'react-intl';
+
+import Field from 'components/admin/forms/Field';
+import FormRow from 'components/admin/forms/FormRow';
+import VariableSelection from 'components/admin/forms/VariableSelection';
+
+const EmailRecipientsFromVariable = () => {
+  const [fieldProps, , fieldHelpers] = useField('toEmailsFromVariable');
+  const {setValue} = fieldHelpers;
+  return (
+    <FormRow>
+      <Field
+        name="toEmailsFromVariable"
+        label={
+          <FormattedMessage
+            description="Email registration options 'toEmailsFromVariable' label"
+            defaultMessage="Using a variable to decide to which email address the
+            submission details will be sent"
+          />
+        }
+        helpText={
+          <FormattedMessage
+            description="Email registration options 'toEmailsFromVariable' helpText"
+            defaultMessage="The email address described in this variable will be used
+            for the mailing. If a variable is selected, the general registration
+            addresses will be used as fallback option. "
+          />
+        }
+      >
+        <VariableSelection
+          name="toEmailsFromVariable"
+          value={fieldProps.value}
+          onChange={event => {
+            setValue(event.target.value);
+          }}
+        />
+      </Field>
+    </FormRow>
+  );
+};
+
+EmailRecipientsFromVariable.propTypes = {};
+
+export default EmailRecipientsFromVariable;

src/openforms/js/lang/en.json

@@ -2524,6 +2524,11 @@
     "description": "\"variable\" operand type",
     "originalDefault": "the variable"
   },
+  "mOh/pF": {
+    "defaultMessage": "The email address described in this variable will be used for the mailing. If a variable is selected, the general registration addresses will be used as fallback option.",
+    "description": "Email registration options 'toEmailsFromVariable' helpText",
+    "originalDefault": "The email address described in this variable will be used for the mailing. If a variable is selected, the general registration addresses will be used as fallback option."
+  },
   "mOjKcm": {
     "defaultMessage": "Steps and fields",
     "description": "Form design tab title",
@@ -2914,6 +2919,11 @@
     "description": "History link button",
     "originalDefault": "History"
   },
+  "uwCD8e": {
+    "defaultMessage": "Using a variable to decide to which email address the submission details will be sent",
+    "description": "Email registration options 'toEmailsFromVariable' label",
+    "originalDefault": "Using a variable to decide to which email address the submission details will be sent"
+  },
   "vAZDY4": {
     "defaultMessage": "Source path",
     "description": "Prefill / Objects API: column header for object type property selection",

src/openforms/js/lang/nl.json

@@ -2545,6 +2545,11 @@
     "description": "\"variable\" operand type",
     "originalDefault": "the variable"
   },
+  "mOh/pF": {
+    "defaultMessage": "The email address described in this variable will be used for the mailing. If a variable is selected, the general registration addresses will be used as fallback option.",
+    "description": "Email registration options 'toEmailsFromVariable' helpText",
+    "originalDefault": "The email address described in this variable will be used for the mailing. If a variable is selected, the general registration addresses will be used as fallback option."
+  },
   "mOjKcm": {
     "defaultMessage": "Stappen en velden",
     "description": "Form design tab title",
@@ -2935,6 +2940,11 @@
     "description": "History link button",
     "originalDefault": "History"
   },
+  "uwCD8e": {
+    "defaultMessage": "Using a variable to decide to which email address the submission details will be sent",
+    "description": "Email registration options 'toEmailsFromVariable' label",
+    "originalDefault": "Using a variable to decide to which email address the submission details will be sent"
+  },
   "vAZDY4": {
     "defaultMessage": "Bronpad",
     "description": "Prefill / Objects API: column header for object type property selection",

src/openforms/registrations/contrib/email/config.py

@@ -13,11 +13,40 @@
 from .constants import AttachmentFormat
 
 
+class Options(TypedDict):
+    """
+    Shape of the email registration plugin options.
+
+    This describes the shape of :attr:`EmailOptionsSerializer.validated_data`, after
+    the input data has been cleaned/validated.
+    """
+
+    to_emails: NotRequired[list[str]]
+    to_emails_from_variable: NotRequired[str]
+    attachment_formats: NotRequired[list[AttachmentFormat | str]]
+    payment_emails: NotRequired[list[str]]
+    attach_files_to_email: bool | None
+    email_subject: NotRequired[str]
+    email_payment_subject: NotRequired[str]
+    email_content_template_html: NotRequired[str]
+    email_content_template_text: NotRequired[str]
+
+
 class EmailOptionsSerializer(JsonSchemaSerializerMixin, serializers.Serializer):
     to_emails = serializers.ListField(
         child=serializers.EmailField(),
         label=_("The email addresses to which the submission details will be sent"),
-        required=True,
+        required=False,  # Either to_emails or to_emails_from_variable should be required
+    )
+    to_emails_from_variable = serializers.CharField(
+        label=_("Key of the target variable containing the email address"),
+        required=False,
+        allow_blank=True,
+        help_text=_(
+            "Key of the target variable whose value will be used for the mailing. "
+            "When using this field, the mailing will only be send to this email address. "
+            "The email addresses field would then be ignored. "
+        ),
     )
     attachment_formats = serializers.ListField(
         child=serializers.ChoiceField(choices=AttachmentFormat.choices),
@@ -99,23 +128,19 @@ class Meta:
             ),
         ]
 
+    def validate(self, attrs: Options) -> Options:
+        # The email registration requires either `to_emails` or `to_emails_from_variable`
+        # to determine which email address to use.
+        # Both may be set - in that case, `to_emails_from_variable` is preferred.
+        if not attrs.get("to_emails") and not attrs.get("to_emails_from_variable"):
+            raise serializers.ValidationError(
+                {
+                    "to_emails": _("This field is required."),
+                },
+                code="required",
+            )
 
-class Options(TypedDict):
-    """
-    Shape of the email registration plugin options.
-
-    This describes the shape of :attr:`EmailOptionsSerializer.validated_data`, after
-    the input data has been cleaned/validated.
-    """
-
-    to_emails: list[str]
-    attachment_formats: NotRequired[list[AttachmentFormat | str]]
-    payment_emails: NotRequired[list[str]]
-    attach_files_to_email: bool | None
-    email_subject: NotRequired[str]
-    email_payment_subject: NotRequired[str]
-    email_content_template_html: NotRequired[str]
-    email_content_template_text: NotRequired[str]
+        return attrs
 
 
 # sanity check for development - keep serializer and type definitions in sync

src/openforms/registrations/contrib/email/plugin.py

@@ -3,6 +3,8 @@
 from typing import Any
 
 from django.conf import settings
+from django.core.exceptions import ValidationError
+from django.core.validators import validate_email
 from django.urls import reverse
 from django.utils import timezone
 from django.utils.translation import get_language_info, gettext_lazy as _
@@ -42,11 +44,41 @@ class EmailRegistration(BasePlugin[Options]):
     verbose_name = _("Email registration")
     configuration_options = EmailOptionsSerializer
 
+    def get_recipients(self, submission: Submission, options: Options) -> list[str]:
+        state = submission.load_submission_value_variables_state()
+        recipients = []
+
+        # If the 'recipients from variable' is used and it exists
+        if (
+            (variable_key := options.get("to_emails_from_variable"))
+            and variable_key in state.variables
+            and (variable_value := state.variables[variable_key].value)
+        ):
+            # To simplify things, treat all variable values as lists
+            if type(variable_value) != list:
+                variable_value = [variable_value]
+
+            # Only if all email addresses are valid, they will be used as recipients
+            try:
+                for value in variable_value:
+                    validate_email(value)
+            except ValidationError:
+                pass
+            else:
+                recipients = variable_value
+
+        # If the variable cannot be used, fallback to the general email addresses
+        if not recipients and "to_emails" in options:
+            recipients = options["to_emails"]
+
+        return recipients
+
     def register_submission(self, submission: Submission, options: Options) -> None:
         config = EmailConfig.get_solo()
         config.apply_defaults_to(options)
 
-        self.send_registration_email(options["to_emails"], submission, options)
+        recipients = self.get_recipients(submission, options)
+        self.send_registration_email(recipients, submission, options)
 
         # ensure that the payment email is also sent if registration is deferred until
         # payment is completed
@@ -187,8 +219,9 @@ def send_registration_email(
 
     def update_payment_status(self, submission: "Submission", options: Options):
         recipients = options.get("payment_emails")
+
         if not recipients:
-            recipients = options["to_emails"]
+            recipients = self.get_recipients(submission, options)
 
         order_ids = submission.payments.get_completed_public_order_ids()
         extra_context = {