Health Check

Monitor mailer health using @nestjs/terminus.

Setup

Install terminus:

pnpm add @nestjs/terminus

Usage

Inject MailerHealthIndicator in your health controller:

import { Controller, Get } from '@nestjs/common';
import { HealthCheck, HealthCheckService } from '@nestjs/terminus';
import { MailerHealthIndicator } from '@nestjs-modules/mailer';

@Controller('health')
export class HealthController {
  constructor(
    private health: HealthCheckService,
    private mailerHealth: MailerHealthIndicator,
  ) {}

  @Get()
  @HealthCheck()
  check() {
    return this.health.check([
      () => this.mailerHealth.isHealthy('mailer'),
    ]);
  }
}

Response

{
  "status": "ok",
  "info": {
    "mailer": {
      "status": "up",
      "transporters": "up"
    }
  }
}

If verifying the transporters throws, the indicator reports "transporters": "down" and logs the error through Nest's Logger. The error message is not included in the response, because it can contain SMTP hosts or credentials and health endpoints are often public.

With Queue

If MailerQueueModule is imported, the health check also reports queue metrics:

{
  "status": "ok",
  "info": {
    "mailer": {
      "status": "up",
      "transporters": "up",
      "queue": {
        "status": "up",
        "waiting": 3,
        "active": 1,
        "completed": 245,
        "failed": 2,
        "delayed": 0
      }
    }
  }
}

Custom Health Key

// Use a custom key for the health response
await this.mailerHealth.isHealthy('email-service');

tip

MailerHealthIndicator is automatically available when you import MailerModule. No additional configuration needed. It uses the existing verifyAllTransporters() method to check SMTP connectivity.