diff --git a/features/email/backend/src/app.module.ts b/features/email/backend/src/app.module.ts
index 84b3e35db..435fd5cd9 100644
--- a/features/email/backend/src/app.module.ts
+++ b/features/email/backend/src/app.module.ts
@@ -11,6 +11,7 @@ import { OrdersModule } from './orders/orders.module'
 import { UsersEmailModule } from './users/users-email.module'
 import { EmployeesModule } from './employees/employees.module'
 import { AdminModule } from './admin/admin.module'
+import { InternalModule } from './internal/internal.module'
 import { HealthController } from './health.controller'
 
 @Module({
@@ -75,6 +76,7 @@ import { HealthController } from './health.controller'
     UsersEmailModule,
     EmployeesModule,
     AdminModule,
+    InternalModule,
   ],
   controllers: [HealthController],
 })
diff --git a/features/email/backend/src/internal/internal.controller.ts b/features/email/backend/src/internal/internal.controller.ts
new file mode 100644
index 000000000..62c7b7a3c
--- /dev/null
+++ b/features/email/backend/src/internal/internal.controller.ts
@@ -0,0 +1,176 @@
+import {
+  Controller,
+  Post,
+  Body,
+  Headers,
+  UnauthorizedException,
+  Logger,
+} from '@nestjs/common'
+import { ConfigService } from '@nestjs/config'
+import { ApiTags, ApiOperation, ApiHeader } from '@nestjs/swagger'
+
+import { UsersEmailService } from '../users/users-email.service'
+import { EmailQueueService } from '../core/email-queue.service'
+import { EmailCategory } from '../core/entities/email-log.entity'
+
+/**
+ * Internal API for service-to-service email requests.
+ * Protected by X-Internal-Api-Key header.
+ */
+@ApiTags('Internal')
+@Controller('internal')
+export class InternalController {
+  private readonly logger = new Logger(InternalController.name)
+  private readonly internalApiKey: string
+
+  constructor(
+    private readonly usersEmailService: UsersEmailService,
+    private readonly emailQueue: EmailQueueService,
+    private readonly configService: ConfigService
+  ) {
+    this.internalApiKey = this.configService.get('INTERNAL_API_KEY', '')
+  }
+
+  private validateApiKey(apiKey: string | undefined): void {
+    if (!this.internalApiKey) {
+      this.logger.warn('INTERNAL_API_KEY not configured - internal API disabled')
+      throw new UnauthorizedException('Internal API not configured')
+    }
+    if (apiKey !== this.internalApiKey) {
+      throw new UnauthorizedException('Invalid API key')
+    }
+  }
+
+  @Post('send/welcome')
+  @ApiOperation({ summary: 'Send welcome email to new user' })
+  @ApiHeader({ name: 'X-Internal-Api-Key', required: true })
+  async sendWelcome(
+    @Headers('x-internal-api-key') apiKey: string,
+    @Body() body: { userId: string; email: string; name?: string }
+  ): Promise<{ jobId: string }> {
+    this.validateApiKey(apiKey)
+    this.logger.log(`Internal request: welcome email for ${body.email}`)
+
+    const jobId = await this.usersEmailService.sendWelcomeEmail(body)
+    return { jobId }
+  }
+
+  @Post('send/verification')
+  @ApiOperation({ summary: 'Send email verification link' })
+  @ApiHeader({ name: 'X-Internal-Api-Key', required: true })
+  async sendVerification(
+    @Headers('x-internal-api-key') apiKey: string,
+    @Body()
+    body: { userId: string; email: string; name?: string; verificationToken: string }
+  ): Promise<{ jobId: string }> {
+    this.validateApiKey(apiKey)
+    this.logger.log(`Internal request: verification email for ${body.email}`)
+
+    const jobId = await this.usersEmailService.sendEmailVerification(body)
+    return { jobId }
+  }
+
+  @Post('send/password-reset')
+  @ApiOperation({ summary: 'Send password reset link' })
+  @ApiHeader({ name: 'X-Internal-Api-Key', required: true })
+  async sendPasswordReset(
+    @Headers('x-internal-api-key') apiKey: string,
+    @Body() body: { userId: string; email: string; name?: string; resetToken: string }
+  ): Promise<{ jobId: string }> {
+    this.validateApiKey(apiKey)
+    this.logger.log(`Internal request: password reset for ${body.email}`)
+
+    const jobId = await this.usersEmailService.sendPasswordReset(body)
+    return { jobId }
+  }
+
+  @Post('send/password-changed')
+  @ApiOperation({ summary: 'Send password changed confirmation' })
+  @ApiHeader({ name: 'X-Internal-Api-Key', required: true })
+  async sendPasswordChanged(
+    @Headers('x-internal-api-key') apiKey: string,
+    @Body() body: { userId: string; email: string; name?: string }
+  ): Promise<{ jobId: string }> {
+    this.validateApiKey(apiKey)
+    this.logger.log(`Internal request: password changed for ${body.email}`)
+
+    const jobId = await this.usersEmailService.sendPasswordChanged(body)
+    return { jobId }
+  }
+
+  @Post('send/account-locked')
+  @ApiOperation({ summary: 'Send account locked notification' })
+  @ApiHeader({ name: 'X-Internal-Api-Key', required: true })
+  async sendAccountLocked(
+    @Headers('x-internal-api-key') apiKey: string,
+    @Body()
+    body: {
+      userId: string
+      email: string
+      name?: string
+      reason?: string
+      unlockUrl?: string
+    }
+  ): Promise<{ jobId: string }> {
+    this.validateApiKey(apiKey)
+    this.logger.log(`Internal request: account locked for ${body.email}`)
+
+    const jobId = await this.usersEmailService.sendAccountLocked(body)
+    return { jobId }
+  }
+
+  @Post('send/login-alert')
+  @ApiOperation({ summary: 'Send new login alert' })
+  @ApiHeader({ name: 'X-Internal-Api-Key', required: true })
+  async sendLoginAlert(
+    @Headers('x-internal-api-key') apiKey: string,
+    @Body()
+    body: {
+      userId: string
+      email: string
+      name?: string
+      device?: string
+      location?: string
+      ipAddress?: string
+    }
+  ): Promise<{ jobId: string }> {
+    this.validateApiKey(apiKey)
+    this.logger.log(`Internal request: login alert for ${body.email}`)
+
+    const jobId = await this.usersEmailService.sendLoginAlert(body)
+    return { jobId }
+  }
+
+  @Post('send/otp')
+  @ApiOperation({ summary: 'Send OTP code for MFA' })
+  @ApiHeader({ name: 'X-Internal-Api-Key', required: true })
+  async sendOtp(
+    @Headers('x-internal-api-key') apiKey: string,
+    @Body()
+    body: {
+      userId: string
+      email: string
+      name?: string
+      code: string
+      expiresInMinutes?: number
+    }
+  ): Promise<{ jobId: string }> {
+    this.validateApiKey(apiKey)
+    this.logger.log(`Internal request: OTP for ${body.email}`)
+
+    const jobId = await this.emailQueue.queueEmail({
+      to: body.email,
+      templateName: 'otp-code',
+      variables: {
+        name: body.name || 'there',
+        code: body.code,
+        expiresIn: `${body.expiresInMinutes || 10} minutes`,
+      },
+      category: EmailCategory.USERS,
+      userId: body.userId,
+      priority: 'high',
+    })
+
+    return { jobId }
+  }
+}
diff --git a/features/email/backend/src/internal/internal.module.ts b/features/email/backend/src/internal/internal.module.ts
new file mode 100644
index 000000000..9c084273e
--- /dev/null
+++ b/features/email/backend/src/internal/internal.module.ts
@@ -0,0 +1,15 @@
+import { Module } from '@nestjs/common'
+
+import { CoreModule } from '../core/core.module'
+import { UsersEmailModule } from '../users/users-email.module'
+import { InternalController } from './internal.controller'
+
+/**
+ * Internal API module for service-to-service communication.
+ * Provides endpoints that other platform services can call to send emails.
+ */
+@Module({
+  imports: [CoreModule, UsersEmailModule],
+  controllers: [InternalController],
+})
+export class InternalModule {}
diff --git a/features/email/backend/templates/users/otp-code.hbs b/features/email/backend/templates/users/otp-code.hbs
new file mode 100644
index 000000000..f7bbfd322
--- /dev/null
+++ b/features/email/backend/templates/users/otp-code.hbs
@@ -0,0 +1,24 @@
+{{!-- templates/users/otp-code.hbs --}}
+{{!-- Variables: name, code, expiresIn --}}
+
+<h1>Your Verification Code</h1>
+
+<p>Hi {{name}},</p>
+
+<p>Here's your one-time verification code:</p>
+
+<div style="background: linear-gradient(135deg, #FF69B4 0%, #FF1493 100%); color: white; font-size: 32px; font-weight: bold; letter-spacing: 8px; text-align: center; padding: 24px 40px; border-radius: 12px; margin: 24px 0;">
+  {{code}}
+</div>
+
+<p>This code will expire in <strong>{{expiresIn}}</strong>.</p>
+
+<p style="color: #666; font-size: 14px;">
+  If you didn't request this code, you can safely ignore this email.
+  Someone may have entered your email address by mistake.
+</p>
+
+<p style="color: #666; font-size: 14px; margin-top: 24px;">
+  <strong>Security tip:</strong> Never share this code with anyone.
+  Lilith staff will never ask for your verification code.
+</p>