fix(backend): log mail delivery failures

backend/src/services/__tests__/mailerService.test.ts

@@ -0,0 +1,56 @@
+import logger from '../../utils/logger.js';
+import { MailerService } from '../notifications/mailerService.js';
+
+const smtpKeys = ['SMTP_HOST', 'SMTP_USER', 'SMTP_PASS', 'SMTP_PORT', 'SMTP_SECURE', 'SMTP_FROM'] as const;
+
+describe('MailerService', () => {
+  const originalEnv = { ...process.env };
+
+  beforeEach(() => {
+    jest.restoreAllMocks();
+    for (const key of smtpKeys) delete process.env[key];
+  });
+
+  afterAll(() => {
+    process.env = originalEnv;
+  });
+
+  it('logs a warning when SMTP is not configured', async () => {
+    const warn = jest.spyOn(logger, 'warn').mockImplementation(() => undefined);
+
+    await MailerService.sendMail({
+      to: ['recipient@example.com'],
+      subject: 'password-reset',
+      text: 'Reset requested',
+    });
+
+    expect(warn).toHaveBeenCalledWith(
+      'Email notification skipped: SMTP is not configured',
+      expect.objectContaining({
+        recipients: ['recipient@example.com'],
+        mailType: 'password-reset',
+      }),
+    );
+  });
+
+  it('logs an error when nodemailer cannot be loaded', async () => {
+    process.env.SMTP_HOST = 'smtp.example.com';
+    process.env.SMTP_USER = 'mailer@example.com';
+    process.env.SMTP_PASS = 'secret';
+    const error = jest.spyOn(logger, 'error').mockImplementation(() => undefined);
+
+    await MailerService.sendMail({
+      to: ['recipient@example.com'],
+      subject: 'payroll-notification',
+      text: 'Payroll ready',
+    });
+
+    expect(error).toHaveBeenCalledWith(
+      'Email notification skipped: nodemailer could not be loaded',
+      expect.objectContaining({
+        recipients: ['recipient@example.com'],
+        mailType: 'payroll-notification',
+      }),
+    );
+  });
+});

backend/src/services/notifications/mailerService.ts

@@ -1,3 +1,5 @@
+import logger from '../../utils/logger.js';
+
 export interface SendMailInput {
   to: string[];
   subject: string;
@@ -10,12 +12,23 @@ export class MailerService {
   }
 
   static async sendMail(input: SendMailInput): Promise<void> {
-    if (!this.isConfigured()) return;
+    if (!this.isConfigured()) {
+      logger.warn('Email notification skipped: SMTP is not configured', {
+        recipients: input.to,
+        mailType: input.subject,
+      });
+      return;
+    }
 
     let nodemailer: any;
     try {
       nodemailer = (await import('nodemailer')).default;
-    } catch {
+    } catch (error) {
+      logger.error('Email notification skipped: nodemailer could not be loaded', {
+        error: error instanceof Error ? error.message : String(error),
+        recipients: input.to,
+        mailType: input.subject,
+      });
       return;
     }
 
@@ -31,11 +44,20 @@ export class MailerService {
 
     const from = process.env.SMTP_FROM || process.env.SMTP_USER;
 
-    await transporter.sendMail({
-      from,
-      to: input.to.join(','),
-      subject: input.subject,
-      text: input.text,
-    });
+    try {
+      await transporter.sendMail({
+        from,
+        to: input.to.join(','),
+        subject: input.subject,
+        text: input.text,
+      });
+    } catch (error) {
+      logger.error('Email notification failed', {
+        error: error instanceof Error ? error.message : String(error),
+        recipients: input.to,
+        mailType: input.subject,
+      });
+      throw error;
+    }
   }
 }