To let Apollo Portal send transactional messages—such as password-reset links, account-activation tokens, or system alerts—you can wire an SMTP relay into the application. The walkthrough below assumes Spring Boot 3.x and uses the JavaMail abstraction provided by spring-boot-starter-mail.

1. Bring in the Mail Starter

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-mail</artifactId>
</dependency>

2. Externalize Connection Settings

Place the following keys in application.yml (or application.properties if you prefer):

spring:
  mail:
    host: smtp.acme.io
    port: 587
    username: noreply@acme.io
    password: ${MAIL_PASSWORD}           # Prefer an env variable or vault
    properties:
      mail:
        smtp:
          auth: true
          starttls:
            enable: true
          ssl:
            trust: smtp.acme.io

3. Programmatic Mail-Sender Bean

Create a dedicated configuration clas sothat the mail client is assembled once and reused everywhere:

@Configuration
public class SmtpConfig {

    @Bean
    public JavaMailSender mailSender(Environment env) {
        JavaMailSenderImpl sender = new JavaMailSenderImpl();
        sender.setHost(env.getRequiredProperty("spring.mail.host"));
        sender.setPort(env.getRequiredProperty("spring.mail.port", Integer.class));
        sender.setUsername(env.getRequiredProperty("spring.mail.username"));
        sender.setPassword(env.getRequiredProperty("spring.mail.password"));

        Properties extra = sender.getJavaMailProperties();
        extra.put("mail.smtp.auth", "true");
        extra.put("mail.smtp.starttls.enable", "true");
        extra.put("mail.debug", "false");   // flip to true while debugging
        return sender;
    }
}

4. Reusable Mail Dispatch Service

Encapsulate the sending logic in a single component so controllers and schedulers can trigger emails without repeating boilerplate:

@Service
public class PortalNotifier {

    private final JavaMailSender mailSender;

    public PortalNotifier(JavaMailSender mailSender) {
        this.mailSender = mailSender;
    }

    public void sendPlain(String recipient, String title, String body) {
        SimpleMailMessage msg = new SimpleMailMessage();
        msg.setTo(recipient);
        msg.setSubject(title);
        msg.setText(body);
        mailSender.send(msg);
    }

    public void sendHtml(String recipient, String title, String html) throws MessagingException {
        MimeMessage mime = mailSender.createMimeMessage();
        MimeMessageHelper helper = new MimeMessageHelper(mime, "utf-8");
        helper.setTo(recipient);
        helper.setSubject(title);
        helper.setText(html, true);
        mailSender.send(mime);
    }
}

5. Hooking It into Apollo Portal

Whenever a controller needs to notify a user—e.g., after a successful password-reset request—inject PortalNotifier and call:

notifier.sendPlain(user.getEmail(),
                   "Reset your Apollo Portal password",
                   "Click the link: " + resetUrl);

The same service can be extended to support attachments, inline images, or templated HTML bodies by leveraging MimeMessageHelper and a template engine such as Thymeleaf or FreeMarker.