feat(connector): enable custom headers for SMTP connector

.changeset/slow-boxes-greet.md

@@ -0,0 +1,5 @@
+---
+"@logto/connector-smtp": minor
+---
+
+enable static custom headers for SMTP connector

packages/connectors/connector-smtp/src/constant.ts

@@ -198,5 +198,14 @@ export const defaultMetadata: ConnectorMetadata = {
       type: ConnectorConfigFormItemType.Switch,
       required: false,
     },
+    {
+      key: 'customHeaders',
+      label: 'Custom Headers',
+      type: ConnectorConfigFormItemType.Json,
+      required: false,
+      defaultValue: {},
+      description:
+        'Custom headers to be added to original email headers when sending messages. Both keys and values should be string-typed.',
+    },
   ],
 };

packages/connectors/connector-smtp/src/index.test.ts

@@ -79,6 +79,28 @@ describe('SMTP connector', () => {
       to: 'baz',
     });
   });
+
+  it('should send mail with customer headers', async () => {
+    const connector = await createConnector({
+      getConfig: vi.fn().mockResolvedValue({
+        ...mockedConfig,
+        customHeaders: { 'X-Test': 'test', 'X-Test-Another': ['test1', 'test2', 'test3'] },
+      }),
+    });
+    await connector.sendMessage({
+      to: 'baz',
+      type: TemplateType.OrganizationInvitation,
+      payload: { code: '345678', link: 'https://example.com' },
+    });
+
+    expect(sendMail).toHaveBeenCalledWith({
+      from: '<notice@test.smtp>',
+      subject: 'Organization invitation',
+      text: 'This is for organization invitation. Your link is https://example.com.',
+      to: 'baz',
+      headers: { 'X-Test': 'test', 'X-Test-Another': ['test1', 'test2', 'test3'] },
+    });
+  });
 });
 
 describe('Test config guard', () => {

packages/connectors/connector-smtp/src/index.ts

@@ -1,4 +1,4 @@
-import { assert } from '@silverhand/essentials';
+import { assert, conditional } from '@silverhand/essentials';
 
 import type {
   GetConnectorConfig,
@@ -14,6 +14,7 @@ import {
   replaceSendMessageHandlebars,
 } from '@logto/connector-kit';
 import nodemailer from 'nodemailer';
+import type Mail from 'nodemailer/lib/mailer';
 import type SMTPTransport from 'nodemailer/lib/smtp-transport';
 
 import { defaultMetadata } from './constant.js';
@@ -44,11 +45,17 @@ const sendMessage =
       template.contentType
     );
 
-    const mailOptions = {
+    const mailOptions: Mail.Options = {
       to,
       from: config.fromEmail,
       replyTo: config.replyTo,
       subject: replaceSendMessageHandlebars(template.subject, payload),
+      ...conditional(
+        config.customHeaders &&
+          Object.entries(config.customHeaders).length > 0 && {
+            headers: config.customHeaders,
+          }
+      ),
       ...contentsObject,
     };
 

packages/connectors/connector-smtp/src/mock.ts

@@ -35,6 +35,7 @@ export const mockedConfig = {
       usageType: 'OrganizationInvitation',
     },
   ],
+  customHeaders: {},
 };
 
 export const mockedOauth2AuthWithToken = {

packages/connectors/connector-smtp/src/types.ts

@@ -125,6 +125,7 @@ export const smtpConfigGuard = z.object({
   servername: z.string().optional(),
   ignoreTLS: z.boolean().optional(),
   requireTLS: z.boolean().optional(),
+  customHeaders: z.record(z.string().or(z.string().array())).optional(),
 });
 
 export type SmtpConfig = z.infer<typeof smtpConfigGuard>;