feat: Add support for custom email recipients in workflow steps

apps/api/src/jobs/email-processor.ts

@@ -117,10 +117,25 @@ export async function createEmailWorker() {
         const fromName = email.fromName || email.project.name;
         const fromEmail = email.from;
 
+        // Parse custom headers from JSON
+        const customHeaders =
+          email.headers && typeof email.headers === 'object' && !Array.isArray(email.headers)
+            ? (email.headers as Record<string, string>)
+            : undefined;
+
+        // Check for custom recipient override in headers
+        const recipientEmail = customHeaders?.['X-Plunk-Recipient-Override'] || email.contact.email;
+
+        // Remove internal headers before sending
+        const publicHeaders = customHeaders ? {...customHeaders} : undefined;
+        if (publicHeaders && 'X-Plunk-Recipient-Override' in publicHeaders) {
+          delete publicHeaders['X-Plunk-Recipient-Override'];
+        }
+
         // Build recipient with name if available
         const recipient: {name?: string; email: string} | string = email.toName
-          ? {name: email.toName, email: email.contact.email}
-          : email.contact.email;
+          ? {name: email.toName, email: recipientEmail}
+          : recipientEmail;
 
         // Determine tracking based on project settings and email type
         const shouldTrack = EmailService.shouldTrackEmail(email.project.tracking, email.sourceType);
@@ -137,6 +152,7 @@ export async function createEmailWorker() {
             html: compiledHtml,
           },
           reply: email.replyTo || undefined,
+          headers: publicHeaders,
           tracking: shouldTrack,
           attachments: email.attachments as {filename: string; content: string; contentType: string}[] | null,
         });

apps/api/src/services/EmailService.ts

@@ -35,6 +35,7 @@ interface SendEmailParams {
   campaignId?: string;
   workflowExecutionId?: string;
   workflowStepExecutionId?: string;
+  recipientEmail?: string; // Optional custom recipient email (overrides contact.email)
 }
 
 /**
@@ -193,7 +194,8 @@ export class EmailService {
 
     // Check subscription status for marketing emails
     // Transactional emails should always be sent regardless of subscription status
-    if (sourceType !== EmailSourceType.TRANSACTIONAL) {
+    // Custom recipient emails also bypass subscription checks (they're not in the contact list)
+    if (sourceType !== EmailSourceType.TRANSACTIONAL && !params.recipientEmail) {
       const contact = await prisma.contact.findUnique({
         where: {id: params.contactId},
         select: {subscribed: true},
@@ -242,6 +244,12 @@ export class EmailService {
       signale.warn(`[BILLING_LIMIT] ${limitCheck.message}`);
     }
 
+    // If custom recipient email is provided, store it in headers for later use
+    const emailHeaders = params.headers ? {...params.headers} : {};
+    if (params.recipientEmail) {
+      emailHeaders['X-Plunk-Recipient-Override'] = params.recipientEmail;
+    }
+
     const email = await prisma.email.create({
       data: {
         projectId: params.projectId,
@@ -251,7 +259,7 @@ export class EmailService {
         from: params.from,
         fromName: params.fromName,
         replyTo: params.replyTo,
-        headers: params.headers ? toPrismaJson(params.headers) : undefined,
+        headers: Object.keys(emailHeaders).length > 0 ? toPrismaJson(emailHeaders) : undefined,
         attachments: params.attachments ? toPrismaJson(params.attachments) : undefined,
         sourceType,
         templateId: params.templateId,
@@ -361,6 +369,15 @@ export class EmailService {
           ? (email.headers as Record<string, string>)
           : undefined;
 
+      // Check for custom recipient override in headers
+      const recipientEmail = customHeaders?.['X-Plunk-Recipient-Override'] || email.contact.email;
+
+      // Remove internal headers before sending
+      const publicHeaders = customHeaders ? {...customHeaders} : undefined;
+      if (publicHeaders && 'X-Plunk-Recipient-Override' in publicHeaders) {
+        delete publicHeaders['X-Plunk-Recipient-Override'];
+      }
+
       // Parse attachments from JSON
       const attachments =
         email.attachments && Array.isArray(email.attachments)
@@ -376,13 +393,13 @@ export class EmailService {
           name: fromName,
           email: fromEmail,
         },
-        to: [email.contact.email],
+        to: [recipientEmail],
         content: {
           subject: formattedEmail.subject,
           html: compiledHtml,
         },
         reply: email.replyTo || undefined,
-        headers: customHeaders,
+        headers: publicHeaders,
         attachments: attachments,
         tracking: shouldTrack,
       });

apps/api/src/services/WorkflowExecutionService.ts

@@ -519,18 +519,25 @@ export class WorkflowExecutionService {
   }
 
   /**
-   * SEND_EMAIL step - Send an email to the contact
+   * SEND_EMAIL step - Send an email to the contact or a custom recipient
    */
   private static async executeSendEmail(
     step: WorkflowStepWithTemplate,
     execution: WorkflowExecutionWithRelations,
     stepExecution: WorkflowStepExecution,
-    _config: StepConfig,
+    config: StepConfig,
   ): Promise<StepResult> {
     if (!step.template) {
       throw new Error('No template configured for SEND_EMAIL step');
     }
 
+    // Parse step config to get recipient configuration
+    const stepConfig = config && typeof config === 'object' && !Array.isArray(config) ? config : {};
+    const recipientConfig =
+      stepConfig.recipient && typeof stepConfig.recipient === 'object' && !Array.isArray(stepConfig.recipient)
+        ? (stepConfig.recipient as {type?: string; customEmail?: string})
+        : {type: 'CONTACT'};
+
     // Get contact data for variable substitution
     const contact = execution.contact;
     const contactData =
@@ -558,10 +565,20 @@ export class WorkflowExecutionService {
     const renderedSubject = this.renderTemplate(step.template.subject, variables);
     const renderedBody = this.renderTemplate(step.template.body, variables);
 
+    // Determine recipient email
+    let recipientEmail = contact.email;
+    let recipientContactId = contact.id;
+
+    if (recipientConfig.type === 'CUSTOM' && recipientConfig.customEmail) {
+      recipientEmail = recipientConfig.customEmail;
+      // For custom recipients, we don't associate with a contact
+      recipientContactId = contact.id; // Keep original contact for tracking
+    }
+
     // Send email via EmailService
     const email = await EmailService.sendWorkflowEmail({
       projectId: execution.workflow.projectId,
-      contactId: contact.id,
+      contactId: recipientContactId,
       workflowExecutionId: execution.id,
       workflowStepExecutionId: stepExecution.id, // Use stepExecution.id, not step.id
       templateId: step.template.id,
@@ -570,11 +587,15 @@ export class WorkflowExecutionService {
       from: step.template.from,
       fromName: step.template.fromName || undefined,
       replyTo: step.template.replyTo || undefined,
+      // Pass custom recipient email if specified
+      recipientEmail: recipientConfig.type === 'CUSTOM' ? recipientEmail : undefined,
     });
 
     return {
       emailId: email.id,
       sentAt: email.createdAt,
+      recipientType: recipientConfig.type,
+      recipientEmail,
     };
   }