Spring Boot¶

Guide for applications built with Spring Boot 3.x (Java, JVM). Mailexam connects via spring-boot-starter-mail and JavaMailSender auto-configuration.

What you need¶

A Mailexam account and a project with SMTP credentials.
JDK 17+ and a Spring Boot project (via start.spring.io or manually).

Copy from the welcome email (or dashboard) for your project:

YOUR_LOGIN — SMTP login (for example, xxxxx);
YOUR_PASSWORD — SMTP password (a unique pair with the login);
host — YOUR_LOGIN.mailexam.io (matches the login).

1. Dependencies¶

On start.spring.io select Spring Web and Java Mail Sender, or add to build.gradle:

plugins {
    id 'java'
    id 'org.springframework.boot' version '3.4.0'
    id 'io.spring.dependency-management' version '1.1.6'
}

group = 'com.example'
version = '0.0.1-SNAPSHOT'

java {
    toolchain {
        languageVersion = JavaLanguageVersion.of(17)
    }
}

repositories {
    mavenCentral()
}

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-web'
    implementation 'org.springframework.boot:spring-boot-starter-mail'
    testImplementation 'org.springframework.boot:spring-boot-starter-test'
}

For Maven — the same artifacts spring-boot-starter-web and spring-boot-starter-mail.

2. Environment variables¶

.env file for local development (do not commit passwords to git) or variables in Run Configuration / CI:

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

SMTP host in config: ${MAILEXAM_LOGIN}.mailexam.io.

Sender address

MAIL_FROM can be any test address — the message goes to Mailexam, not to a real recipient.

Alternative ports¶

587 + STARTTLS (recommended)252525 without TLS

MAILEXAM_PORT=587

spring.mail.properties.mail.smtp.starttls.enable=true

MAILEXAM_PORT=2525

STARTTLS enabled, same as for 587.

MAILEXAM_PORT=25

spring.mail.properties.mail.smtp.starttls.enable=false

3. Mail configuration¶

src/main/resources/application.yml:

spring:
  mail:
    host: ${MAILEXAM_LOGIN}.mailexam.io
    port: ${MAILEXAM_PORT:587}
    username: ${MAILEXAM_LOGIN}
    password: ${MAILEXAM_PASSWORD}
    properties:
      mail.smtp.auth: true
      mail.smtp.starttls.enable: true

mail:
  from: ${MAIL_FROM:noreply@example.test}

The same in application.properties:

spring.mail.host=${MAILEXAM_LOGIN}.mailexam.io
spring.mail.port=${MAILEXAM_PORT:587}
spring.mail.username=${MAILEXAM_LOGIN}
spring.mail.password=${MAILEXAM_PASSWORD}
spring.mail.properties.mail.smtp.auth=true
spring.mail.properties.mail.smtp.starttls.enable=true
mail.from=${MAIL_FROM:noreply@example.test}

For port 25 override mail.smtp.starttls.enable=false (see table above).

4. Sending service¶

package com.example.demo.mail;

import jakarta.mail.MessagingException;
import jakarta.mail.internet.MimeMessage;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.mail.javamail.JavaMailSender;
import org.springframework.mail.javamail.MimeMessageHelper;
import org.springframework.stereotype.Service;

@Service
public class MailService {

    private final JavaMailSender mailSender;
    private final String from;

    public MailService(JavaMailSender mailSender, @Value("${mail.from}") String from) {
        this.mailSender = mailSender;
        this.from = from;
    }

    public void sendTest(String to, String subject, String body) throws MessagingException {
        MimeMessage message = mailSender.createMimeMessage();
        MimeMessageHelper helper = new MimeMessageHelper(message, "UTF-8");
        helper.setFrom(from);
        helper.setTo(to);
        helper.setSubject(subject);
        helper.setText(body, false);
        mailSender.send(message);
    }
}

5. REST endpoint¶

package com.example.demo.web;

import com.example.demo.mail.MailService;
import jakarta.mail.MessagingException;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;

import java.util.Map;

@RestController
public class MailController {

    private final MailService mailService;

    public MailController(MailService mailService) {
        this.mailService = mailService;
    }

    public record SendRequest(
            String to,
            String subject,
            String body
    ) {
        public SendRequest {
            if (to == null || to.isBlank()) {
                to = "user@example.test";
            }
            if (subject == null || subject.isBlank()) {
                subject = "Spring + Mailexam";
            }
            if (body == null || body.isBlank()) {
                body = "Mailexam test from Spring Boot";
            }
        }
    }

    @PostMapping("/mail/test")
    public Map<String, String> sendTest(@RequestBody SendRequest request) throws MessagingException {
        mailService.sendTest(request.to(), request.subject(), request.body());
        return Map.of("status", "ok");
    }
}

Start and verify:

./gradlew bootRun

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 will appear in the Mailexam dashboard → your project → inbox.

6. Local development and CI¶

Environment	Recommendation
`local`	variables in IDE or `.env` + envfile plugin in Gradle
CI	secrets `MAILEXAM_LOGIN`, `MAILEXAM_PASSWORD` in GitLab CI/CD Variables

Example for .gitlab-ci.yml:

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

After an integration test, verify delivery via the Mailexam API.

7. Common issues¶

TLS or connection error

spring.mail.host must be {login}.mailexam.io, username — the same login from the email.
Login and password are a pair from the email for one project.

Variables not substituted

Run the application with MAILEXAM_LOGIN and MAILEXAM_PASSWORD set; in the IDE check Environment in the Run configuration.

Message not in the dashboard

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