diff --git a/.env.example b/.env.example
index 73e95c394c..ae3537038a 100644
--- a/.env.example
+++ b/.env.example
@@ -625,6 +625,7 @@ EMAIL_PORT=25
 EMAIL_ENCRYPTION=
 EMAIL_ENCRYPTION_HOSTNAME=
 EMAIL_ALLOW_SELFSIGNED=
+# Leave both empty for SMTP servers that do not require authentication
 EMAIL_USERNAME=
 EMAIL_PASSWORD=
 EMAIL_FROM_NAME=
diff --git a/api/server/utils/__tests__/sendEmail.spec.js b/api/server/utils/__tests__/sendEmail.spec.js
new file mode 100644
index 0000000000..5c79094c53
--- /dev/null
+++ b/api/server/utils/__tests__/sendEmail.spec.js
@@ -0,0 +1,143 @@
+const nodemailer = require('nodemailer');
+const { readFileAsString } = require('@librechat/api');
+
+jest.mock('nodemailer');
+jest.mock('@librechat/data-schemas', () => ({
+  logger: { debug: jest.fn(), warn: jest.fn(), error: jest.fn() },
+}));
+jest.mock('@librechat/api', () => ({
+  logAxiosError: jest.fn(),
+  isEnabled: jest.fn((val) => val === 'true' || val === true),
+  readFileAsString: jest.fn(),
+}));
+
+const savedEnv = { ...process.env };
+
+const mockSendMail = jest.fn().mockResolvedValue({ messageId: 'test-id' });
+
+beforeEach(() => {
+  jest.clearAllMocks();
+  process.env = { ...savedEnv };
+  process.env.EMAIL_HOST = 'smtp.example.com';
+  process.env.EMAIL_PORT = '587';
+  process.env.EMAIL_FROM = 'noreply@example.com';
+  process.env.APP_TITLE = 'TestApp';
+  delete process.env.EMAIL_USERNAME;
+  delete process.env.EMAIL_PASSWORD;
+  delete process.env.MAILGUN_API_KEY;
+  delete process.env.MAILGUN_DOMAIN;
+  delete process.env.EMAIL_SERVICE;
+  delete process.env.EMAIL_ENCRYPTION;
+  delete process.env.EMAIL_ENCRYPTION_HOSTNAME;
+  delete process.env.EMAIL_ALLOW_SELFSIGNED;
+
+  readFileAsString.mockResolvedValue({ content: '<p>{{name}}</p>' });
+  nodemailer.createTransport.mockReturnValue({ sendMail: mockSendMail });
+});
+
+afterAll(() => {
+  process.env = savedEnv;
+});
+
+/** Loads a fresh copy of sendEmail so process.env reads are re-evaluated. */
+function loadSendEmail() {
+  jest.resetModules();
+  jest.mock('nodemailer', () => ({
+    createTransport: jest.fn().mockReturnValue({ sendMail: mockSendMail }),
+  }));
+  jest.mock('@librechat/data-schemas', () => ({
+    logger: { debug: jest.fn(), warn: jest.fn(), error: jest.fn() },
+  }));
+  jest.mock('@librechat/api', () => ({
+    logAxiosError: jest.fn(),
+    isEnabled: jest.fn((val) => val === 'true' || val === true),
+    readFileAsString: jest.fn().mockResolvedValue({ content: '<p>{{name}}</p>' }),
+  }));
+  return require('../sendEmail');
+}
+
+const baseParams = {
+  email: 'user@example.com',
+  subject: 'Test',
+  payload: { name: 'User' },
+  template: 'test.handlebars',
+};
+
+describe('sendEmail SMTP auth assembly', () => {
+  it('includes auth when both EMAIL_USERNAME and EMAIL_PASSWORD are set', async () => {
+    process.env.EMAIL_USERNAME = 'smtp_user';
+    process.env.EMAIL_PASSWORD = 'smtp_pass';
+    const sendEmail = loadSendEmail();
+    const { createTransport } = require('nodemailer');
+
+    await sendEmail(baseParams);
+
+    expect(createTransport).toHaveBeenCalledTimes(1);
+    const transporterOptions = createTransport.mock.calls[0][0];
+    expect(transporterOptions.auth).toEqual({
+      user: 'smtp_user',
+      pass: 'smtp_pass',
+    });
+  });
+
+  it('omits auth when both EMAIL_USERNAME and EMAIL_PASSWORD are absent', async () => {
+    const sendEmail = loadSendEmail();
+    const { createTransport } = require('nodemailer');
+
+    await sendEmail(baseParams);
+
+    expect(createTransport).toHaveBeenCalledTimes(1);
+    const transporterOptions = createTransport.mock.calls[0][0];
+    expect(transporterOptions.auth).toBeUndefined();
+  });
+
+  it('omits auth and logs a warning when only EMAIL_USERNAME is set', async () => {
+    process.env.EMAIL_USERNAME = 'smtp_user';
+    const sendEmail = loadSendEmail();
+    const { createTransport } = require('nodemailer');
+    const { logger: freshLogger } = require('@librechat/data-schemas');
+
+    await sendEmail(baseParams);
+
+    const transporterOptions = createTransport.mock.calls[0][0];
+    expect(transporterOptions.auth).toBeUndefined();
+    expect(freshLogger.warn).toHaveBeenCalledWith(
+      expect.stringContaining('EMAIL_USERNAME and EMAIL_PASSWORD must both be set'),
+    );
+  });
+
+  it('omits auth and logs a warning when only EMAIL_PASSWORD is set', async () => {
+    process.env.EMAIL_PASSWORD = 'smtp_pass';
+    const sendEmail = loadSendEmail();
+    const { createTransport } = require('nodemailer');
+    const { logger: freshLogger } = require('@librechat/data-schemas');
+
+    await sendEmail(baseParams);
+
+    const transporterOptions = createTransport.mock.calls[0][0];
+    expect(transporterOptions.auth).toBeUndefined();
+    expect(freshLogger.warn).toHaveBeenCalledWith(
+      expect.stringContaining('EMAIL_USERNAME and EMAIL_PASSWORD must both be set'),
+    );
+  });
+
+  it('does not log a warning when both credentials are properly set', async () => {
+    process.env.EMAIL_USERNAME = 'smtp_user';
+    process.env.EMAIL_PASSWORD = 'smtp_pass';
+    const sendEmail = loadSendEmail();
+    const { logger: freshLogger } = require('@librechat/data-schemas');
+
+    await sendEmail(baseParams);
+
+    expect(freshLogger.warn).not.toHaveBeenCalled();
+  });
+
+  it('does not log a warning when both credentials are absent', async () => {
+    const sendEmail = loadSendEmail();
+    const { logger: freshLogger } = require('@librechat/data-schemas');
+
+    await sendEmail(baseParams);
+
+    expect(freshLogger.warn).not.toHaveBeenCalled();
+  });
+});
diff --git a/api/server/utils/sendEmail.js b/api/server/utils/sendEmail.js
index 432a571ffb..3fa3e6fcba 100644
--- a/api/server/utils/sendEmail.js
+++ b/api/server/utils/sendEmail.js
@@ -124,11 +124,20 @@ const sendEmail = async ({ email, subject, payload, template, throwError = true
         // Whether to accept unsigned certificates
         rejectUnauthorized: !isEnabled(process.env.EMAIL_ALLOW_SELFSIGNED),
       },
-      auth: {
+    };
+
+    const hasUsername = !!process.env.EMAIL_USERNAME;
+    const hasPassword = !!process.env.EMAIL_PASSWORD;
+    if (hasUsername && hasPassword) {
+      transporterOptions.auth = {
         user: process.env.EMAIL_USERNAME,
         pass: process.env.EMAIL_PASSWORD,
-      },
-    };
+      };
+    } else if (hasUsername !== hasPassword) {
+      logger.warn(
+        '[sendEmail] EMAIL_USERNAME and EMAIL_PASSWORD must both be set for authenticated SMTP, or both omitted for unauthenticated SMTP. Proceeding without authentication.',
+      );
+    }
 
     if (process.env.EMAIL_ENCRYPTION_HOSTNAME) {
       // Check the certificate against this name explicitly
diff --git a/packages/api/src/utils/__tests__/email.test.ts b/packages/api/src/utils/__tests__/email.test.ts
new file mode 100644
index 0000000000..ccbd0aabfe
--- /dev/null
+++ b/packages/api/src/utils/__tests__/email.test.ts
@@ -0,0 +1,120 @@
+import { logger } from '@librechat/data-schemas';
+import { checkEmailConfig } from '../email';
+
+jest.mock('@librechat/data-schemas', () => ({
+  logger: { warn: jest.fn() },
+}));
+
+const savedEnv = { ...process.env };
+
+beforeEach(() => {
+  jest.clearAllMocks();
+  process.env = { ...savedEnv };
+  delete process.env.EMAIL_SERVICE;
+  delete process.env.EMAIL_HOST;
+  delete process.env.EMAIL_USERNAME;
+  delete process.env.EMAIL_PASSWORD;
+  delete process.env.EMAIL_FROM;
+  delete process.env.MAILGUN_API_KEY;
+  delete process.env.MAILGUN_DOMAIN;
+});
+
+afterAll(() => {
+  process.env = savedEnv;
+});
+
+describe('checkEmailConfig', () => {
+  describe('SMTP configuration', () => {
+    it('returns true with EMAIL_HOST and EMAIL_FROM (no credentials)', () => {
+      process.env.EMAIL_HOST = 'smtp.example.com';
+      process.env.EMAIL_FROM = 'noreply@example.com';
+      expect(checkEmailConfig()).toBe(true);
+    });
+
+    it('returns true with EMAIL_SERVICE and EMAIL_FROM (no credentials)', () => {
+      process.env.EMAIL_SERVICE = 'gmail';
+      process.env.EMAIL_FROM = 'noreply@example.com';
+      expect(checkEmailConfig()).toBe(true);
+    });
+
+    it('returns true with EMAIL_HOST, EMAIL_FROM, and full credentials', () => {
+      process.env.EMAIL_HOST = 'smtp.example.com';
+      process.env.EMAIL_FROM = 'noreply@example.com';
+      process.env.EMAIL_USERNAME = 'user';
+      process.env.EMAIL_PASSWORD = 'pass';
+      expect(checkEmailConfig()).toBe(true);
+    });
+
+    it('returns false when EMAIL_FROM is missing', () => {
+      process.env.EMAIL_HOST = 'smtp.example.com';
+      expect(checkEmailConfig()).toBe(false);
+    });
+
+    it('returns false when neither EMAIL_HOST nor EMAIL_SERVICE is set', () => {
+      process.env.EMAIL_FROM = 'noreply@example.com';
+      expect(checkEmailConfig()).toBe(false);
+    });
+
+    it('returns false when no email env vars are set', () => {
+      expect(checkEmailConfig()).toBe(false);
+    });
+  });
+
+  describe('partial credential warning', () => {
+    it('logs a warning when only EMAIL_USERNAME is set', () => {
+      process.env.EMAIL_HOST = 'smtp.example.com';
+      process.env.EMAIL_FROM = 'noreply@example.com';
+      process.env.EMAIL_USERNAME = 'user';
+      checkEmailConfig();
+      expect(logger.warn).toHaveBeenCalledWith(
+        expect.stringContaining('EMAIL_USERNAME and EMAIL_PASSWORD must both be set'),
+      );
+    });
+
+    it('logs a warning when only EMAIL_PASSWORD is set', () => {
+      process.env.EMAIL_HOST = 'smtp.example.com';
+      process.env.EMAIL_FROM = 'noreply@example.com';
+      process.env.EMAIL_PASSWORD = 'pass';
+      checkEmailConfig();
+      expect(logger.warn).toHaveBeenCalledWith(
+        expect.stringContaining('EMAIL_USERNAME and EMAIL_PASSWORD must both be set'),
+      );
+    });
+
+    it('does not warn when both credentials are set', () => {
+      process.env.EMAIL_HOST = 'smtp.example.com';
+      process.env.EMAIL_FROM = 'noreply@example.com';
+      process.env.EMAIL_USERNAME = 'user';
+      process.env.EMAIL_PASSWORD = 'pass';
+      checkEmailConfig();
+      expect(logger.warn).not.toHaveBeenCalled();
+    });
+
+    it('does not warn when neither credential is set', () => {
+      process.env.EMAIL_HOST = 'smtp.example.com';
+      process.env.EMAIL_FROM = 'noreply@example.com';
+      checkEmailConfig();
+      expect(logger.warn).not.toHaveBeenCalled();
+    });
+
+    it('does not warn for partial credentials when SMTP is not configured', () => {
+      process.env.EMAIL_USERNAME = 'user';
+      checkEmailConfig();
+      expect(logger.warn).not.toHaveBeenCalled();
+    });
+  });
+
+  describe('Mailgun configuration', () => {
+    it('returns true with Mailgun API key, domain, and EMAIL_FROM', () => {
+      process.env.MAILGUN_API_KEY = 'key-abc123';
+      process.env.MAILGUN_DOMAIN = 'mg.example.com';
+      process.env.EMAIL_FROM = 'noreply@example.com';
+      expect(checkEmailConfig()).toBe(true);
+    });
+
+    it('returns false when Mailgun is partially configured', () => {
+      process.env.MAILGUN_API_KEY = 'key-abc123';
+      expect(checkEmailConfig()).toBe(false);
+    });
+  });
+});
diff --git a/packages/api/src/utils/email.ts b/packages/api/src/utils/email.ts
index f98e7c51be..6f9171a43b 100644
--- a/packages/api/src/utils/email.ts
+++ b/packages/api/src/utils/email.ts
@@ -1,3 +1,5 @@
+import { logger } from '@librechat/data-schemas';
+
 /**
  * Check if email configuration is set
  * @returns Returns `true` if either Mailgun or SMTP is properly configured
@@ -7,10 +9,17 @@ export function checkEmailConfig(): boolean {
     !!process.env.MAILGUN_API_KEY && !!process.env.MAILGUN_DOMAIN && !!process.env.EMAIL_FROM;
 
   const hasSMTPConfig =
-    (!!process.env.EMAIL_SERVICE || !!process.env.EMAIL_HOST) &&
-    !!process.env.EMAIL_USERNAME &&
-    !!process.env.EMAIL_PASSWORD &&
-    !!process.env.EMAIL_FROM;
+    (!!process.env.EMAIL_SERVICE || !!process.env.EMAIL_HOST) && !!process.env.EMAIL_FROM;
+
+  if (hasSMTPConfig) {
+    const hasUsername = !!process.env.EMAIL_USERNAME;
+    const hasPassword = !!process.env.EMAIL_PASSWORD;
+    if (hasUsername !== hasPassword) {
+      logger.warn(
+        '[checkEmailConfig] EMAIL_USERNAME and EMAIL_PASSWORD must both be set for authenticated SMTP, or both omitted for unauthenticated SMTP.',
+      );
+    }
+  }
 
   return hasMailgunConfig || hasSMTPConfig;
 }