Docker Couldn't connect to host, port: smtp-mail.outlook.com, 587

Question

I've created a docker image of a springboot maven application. This application communicate with smtp server to send email through port 587. The app works fine locally, however when I create a docker image and run it, the application breaks when it try to access a socket to send email.

This is how my Dockerfile looks like.

FROM adoptopenjdk:11-jre-hotspot

RUN mkdir /opt/app

ADD target/camunda-fire-alarm.jar camunda-fire-alarm.jar

EXPOSE 8080 587

ENTRYPOINT ["java", "-jar", "camunda-fire-alarm.jar"]

The following are the commands I use to build and run the docker image.

build command:

docker build -f Dockerfile -t camunda-fire-alarm .

run command:

docker run -p 8080:8080 -p 587:587 camunda-fire-alarm

This is the Java code I use to send email from outlook

public static void SendFromOutlook(String from, String pass, String to, String subject, String body) 
{
        final String username = from;  // like yourname@outlook.com
        final String password = pass;   // password here

        Properties props = new Properties();
        props.put("mail.smtp.auth", "true");
        props.put("mail.smtp.starttls.enable", "true");
        props.put("mail.smtp.host", "smtp-mail.outlook.com");
        props.put("mail.smtp.port", "587");

        Session session = Session.getInstance(props,
                new javax.mail.Authenticator() {
                    @Override
                    protected PasswordAuthentication getPasswordAuthentication() {
                        return new PasswordAuthentication(username, password);
                    }
                });
        session.setDebug(true);

        try {

            Message message = new MimeMessage(session);
            message.setFrom(new InternetAddress(username));
            message.setRecipients(Message.RecipientType.TO,
                    InternetAddress.parse(String.valueOf(to)));   // like inzi769@gmail.com
            message.setSubject(subject);
            message.setText(body);

            System.out.println("Sending email to : "+to + " with message < " + body + " >");
            Transport.send(message);

            System.out.println("Done");

        } catch (MessagingException e) {
            throw new RuntimeException(e);
        }
}

EDIT: Stacktrace

 ENGINE-16004 Exception while closing command context: ENGINE-03051 There was an exception while invoking the TaskListener. Message: 'Exception while invoking TaskListener: com.sun.mail.util.MailConnectException: Couldn't connect to host, port: smtp-mail.outlook.com, 587; timeout -1;
  nested exception is:
        java.net.UnknownHostException: smtp-mail.outlook.com'

org.camunda.bpm.engine.ProcessEngineException: ENGINE-03051 There was an exception while invoking the TaskListener. Message: 'Exception while invoking TaskListener: com.sun.mail.util.M
ailConnectException: Couldn't connect to host, port: smtp-mail.outlook.com, 587; timeout -1;
  nested exception is:
        java.net.UnknownHostException: smtp-mail.outlook.com'
        at org.camunda.bpm.engine.impl.db.EnginePersistenceLogger.invokeTaskListenerException(EnginePersistenceLogger.java:449) ~[camunda-engine-7.12.0.jar!/:7.12.0]

Not sure why the docker breaks the application during runtime. I would appreciate any help/guidelines.

Thanks in Advance