Spring Boot + Mailexam

Minimal Spring Boot example that sends test mail through Mailexam SMTP via spring-boot-starter-mail and JavaMailSender.

Based on the Mailexam Spring Boot guide.

What you need

• A Mailexam account and a project with SMTP credentials.
• JDK 17+.

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 (used in application.yml)

Quick start (host)

1. Export environment variables (or copy from .env.example into your shell):

cp .env.example .env
# edit .env, then:
set -a && source .env && set +a

2. Run the application:

./gradlew bootRun

The server listens on http://127.0.0.1:8080 by default.

3. Send a test message:

curl -X POST http://127.0.0.1:8080/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.

Environment variables

Variable	Required	Default	Description
MAILEXAM_LOGIN	yes	—	SMTP login; host is {login}.mailexam.ru
MAILEXAM_PASSWORD	yes	—	SMTP password
MAILEXAM_PORT	no	587	SMTP port (587, 2525, or 25)
MAIL_FROM	no	noreply@example.test	Sender address
HTTP_HOST	no	127.0.0.1	HTTP bind address
HTTP_PORT	no	8080	HTTP listen port

For port 587 STARTTLS is enabled via mail.smtp.starttls.enable=true. For port 25 set spring.mail.properties.mail.smtp.starttls.enable=false.

Project layout

.
├── build.gradle
├── src/main/java/com/example/demo/
│   ├── MailexamSpringApplication.java
│   ├── mail/MailService.java
│   └── web/MailController.java
├── src/main/resources/application.yml
├── .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 ./gradlew bootRun (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://127.0.0.1:8080/mail/test \
  -H 'Content-Type: application/json' \
  -d '{"to":"user@example.test","subject":"Test","body":"Hello"}'

Inside the container the server binds to 0.0.0.0:8080 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.

Troubleshooting

TLS or connection error

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

Variables not substituted

• Export MAILEXAM_LOGIN and MAILEXAM_PASSWORD before ./gradlew bootRun, or set them in your IDE Run configuration.

Message not in the dashboard

• Open the inbox of the same Mailexam project.
• Enable logging: logging.level.org.springframework.mail=DEBUG.

See also

• Mailexam Spring Boot guide (wiki)
• Ktor reference implementation — another JVM framework
• Spring Boot — Sending Email
• Mailexam API documentation