NestJS + Mailexam

Minimal NestJS example that sends test mail through Mailexam SMTP via Nodemailer and @nestjs-modules/mailer.

Based on the Mailexam NestJS guide.

What you need

• A Mailexam account and a project with SMTP credentials.
• Node.js 18+ and npm.

From your Mailexam welcome email or dashboard:

Variable	Description
MAILEXAM_LOGIN	SMTP login (for example, xxxxx)
MAILEXAM_PASSWORD	SMTP password (paired with the login)
Host	{MAILEXAM_LOGIN}.mailexam.ru (built automatically in code)

Quick start (host)

1. Install dependencies:

npm install

2. Copy the example environment file and fill in your credentials:

cp .env.example .env

3. Edit .env:

MAILEXAM_LOGIN=YOUR_LOGIN
MAILEXAM_PASSWORD=YOUR_PASSWORD
MAILEXAM_PORT=587
MAIL_FROM=noreply@example.test

4. Build and run the server:

npm run build
npm start

The server listens on http://127.0.0.1:3000 by default.

5. Send a test message:

curl -X POST http://127.0.0.1:3000/mail/test \
  -H 'Content-Type: application/json' \
  -d '{"to":"user@example.test","subject":"Test","text":"Hello"}'

The message appears in the Mailexam dashboard → your project → inbox.

Environment variables

Variable	Required	Default	Description
MAILEXAM_LOGIN	yes	—	SMTP login; also used to build the host name
MAILEXAM_PASSWORD	yes	—	SMTP password
MAILEXAM_PORT	no	587	SMTP port (587, 2525, or 465)
MAIL_FROM	no	noreply@example.test	Sender address (any test address is fine)
HTTP_HOST	no	127.0.0.1	HTTP bind address
HTTP_PORT	no	3000	HTTP listen port

For port 587 the transport uses STARTTLS (secure: false). For port 465 it uses SMTPS (secure: true).

Project layout

.
├── package.json
├── tsconfig.json
├── src/
│   ├── main.ts           # bootstrap and HTTP server
│   ├── app.module.ts     # MailerModule configuration
│   └── mail.controller.ts
├── .env.example
├── Dockerfile            # for local debugging only
└── docker-compose.yml

Docker (debugging)

Docker is provided for local debugging. For day-to-day development, run the app on the host with npm run build && npm start (see above).

cp .env.example .env
# edit .env with your credentials

docker compose up --build

Then call the same endpoint on the mapped port:

curl -X POST http://127.0.0.1:3000/mail/test \
  -H 'Content-Type: application/json' \
  -d '{"to":"user@example.test","subject":"Test","text":"Hello"}'

Inside the container the server binds to 0.0.0.0:3000 so the port mapping works.

CI

Set these secrets in your CI environment:

variables:
  MAILEXAM_LOGIN: $MAILEXAM_LOGIN
  MAILEXAM_PASSWORD: $MAILEXAM_PASSWORD
  MAILEXAM_PORT: "587"
  MAIL_FROM: "noreply@example.test"

After sending a message in a test, verify delivery via the Mailexam API.

For unit tests mock MailerService or use transport: { jsonTransport: true } in the test module.

Troubleshooting

Connection timeout / authentication failed

• Host must be {login}.mailexam.ru, where {login} matches MAILEXAM_LOGIN.
• Login and password must come from the same Mailexam project.

Port 587 and TLS

• For 587: secure: false (STARTTLS). For 465: secure: true.

Variables undefined

• Add a .env file in the project root or export variables in your shell/CI.

Message not in the dashboard

• Open the inbox of the same Mailexam project.
• Check Nest logs for SMTP errors on sendMail.

Port already in use

• Change HTTP_PORT in .env.

See also

• Mailexam NestJS guide (wiki)
• NestJS documentation
• @nestjs-modules/mailer
• Nodemailer documentation