Phoenix + Mailexam

Minimal Phoenix example that sends test mail through Mailexam SMTP via Swoosh.

Based on the Mailexam Phoenix guide.

What you need

• A Mailexam account and a project with SMTP credentials.
• Elixir 1.15+ and Erlang/OTP 26+.

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/runtime.exs)

Quick start (host)

1. Install dependencies:

mix deps.get

2. Export Mailexam credentials (or copy from the example file):

cp .env.example .env
export $(grep -v '^#' .env | xargs)

3. Edit .env if needed:

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

4. Run the server:

mix phx.server

The server listens on http://127.0.0.1:4000 by default.

5. Send a test message:

curl -X POST http://127.0.0.1:4000/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.

IEx alternative

iex -S mix

Mailexam.TestEmail.deliver("user@example.test", "Phoenix + Mailexam", "Mailexam test from Phoenix")

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	4000	HTTP listen port

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

Project layout

.
├── mix.exs
├── config/runtime.exs              # Mailexam SMTP via Swoosh.Adapters.SMTP
├── lib/mailexam/mailer.ex
├── lib/mailexam/test_email.ex
├── lib/mailexam_web/controllers/mail_controller.ex
├── config/routes via router.ex     # POST /mail/test
├── .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 mix phx.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://127.0.0.1:4000/mail/test \
  -H 'Content-Type: application/json' \
  -d '{"to":"user@example.test","subject":"Test","body":"Hello"}'

Inside the container the server binds to 0.0.0.0:4000.

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.

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

• Requires tls: :always, not :never.

SMTP timeout or :smtp_response error

• Ensure gen_smtp is in dependencies and variables are set before mix phx.server.

Message not in the dashboard

• Open the inbox of the same Mailexam project.
• In dev, enable debug logs: config :logger, level: :debug.

See also

• Mailexam Phoenix guide (wiki)
• Swoosh SMTP adapter
• Mailexam API documentation