Ruby on Rails + Mailexam

Minimal Ruby on Rails example that sends test mail through Mailexam SMTP via Action Mailer.

Based on the Mailexam Ruby on Rails guide.

What you need

• A Mailexam account and a project with SMTP credentials.
• Ruby 3.2+ and Bundler.

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 in config/initializers/mailexam_mailer.rb)

Quick start (host)

1. Install dependencies:

bundle 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. Run the server:

bin/rails server

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","body":"Hello"}'

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

Rails console alternative

bin/rails console

TestMailer.with(
  to: "user@example.test",
  subject: "Ruby on Rails + Mailexam",
  body: "Mailexam test from Rails"
).test_email.deliver_now

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 25)
MAIL_FROM	no	noreply@example.test	Sender address (any test address is fine)
PORT	no	3000	HTTP listen port

For ports 587 and 2525, STARTTLS is enabled (enable_starttls_auto: true). For port 25, it is disabled.

Project layout

.
├── Gemfile
├── config/initializers/mailexam_mailer.rb
├── app/mailers/test_mailer.rb
├── app/controllers/mail_controller.rb
├── config/routes.rb
├── .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 bin/rails server (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","body":"Hello"}'

Inside the container the server binds to 0.0.0.0:3000.

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.

In tests you can use delivery_method = :test and ActionMailer::Base.deliveries.

Troubleshooting

TLS or 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

• enable_starttls_auto must be true.

Environment variables not picked up

• Restart bin/rails server after changing .env.

Message not in the dashboard

• Open the inbox of the same Mailexam project.
• Ensure perform_deliveries = true and the app is not using the :test delivery method.

See also

• Mailexam Ruby on Rails guide (wiki)
• Action Mailer Basics
• Mailexam API documentation