Java Send Mail Example

This sample illustrates how to send smtp emails using a simple Servlet-based Java webapp easily in Cloud Foundry using email providers like SendGrid and MailGun that both have free levels of service that allow you to send up to 200 emails per day and paid plans to do more. The index.jsp of the application presents a form where a user can provide inputs from the mail provider. Note that on Cloud Foundry smtp outbound on port 25 is blocked. But other ports are open, such as the unsecured port 587 or secured port 465.

The form on the index.jsp submits the values to a MailServlet, which uses a MailUtility class to actually attempt to send the email.

Java Mail Code

Here is the relevant code snippet from the MailUtility class that shows this is just standard Java Mail and configuring the smtp provider. No special tricks are required.

        Properties props = new Properties();
        props.put("mail.transport.protocol", "smtp");
        props.put("mail.smtp.host", smtpHost);
        props.put("mail.smtp.auth", "true");
        
    	if( smtpPort == 465 )
    	{
    		props.put("mail.smtp.socketFactory.port", smtpPort);
    		props.put("mail.smtp.socketFactory.class",
    				"javax.net.ssl.SSLSocketFactory");    		
    	}
        else props.put("mail.smtp.port", smtpPort);

    	
        Authenticator auth = new SMTPAuthenticator( smtpAuthUser, smtpAuthPwd );
        Session mailSession = Session.getInstance(props, auth);
        
        // uncomment for debugging infos to stdout
        mailSession.setDebug(true);
        Transport transport = mailSession.getTransport();

        MimeMessage message = new MimeMessage(mailSession);

        message.setText(body);
        message.setFrom(new InternetAddress(from));
        message.setSubject(subject);
        message.addRecipient(Message.RecipientType.TO,
             new InternetAddress(to));

        transport.connect();
        transport.sendMessage(message,
            message.getRecipients(Message.RecipientType.TO));
        transport.close();

Configuring the Application

This step is optional because you can use the index.jsp to override the values at runtime. If you want configure the environment variables with valid email provider information, then it is easiest to edit the manifest.yml file and put in the information from your mail provider.

Here is an example of manifest.yml with SendGrid where the username and password would use your SendGrid username and password.

---
applications:
  .:
    name: mail-java
    framework: java_web
    runtime: java7
    memory: 128M
    instances: 1
    url: mail-${random-word}.${target-base}
    env:
        SMTP_HOST: smtp.sendgrid.net
        SMTP_PORT: 465
        SMTP_AUTH_USER: username
        SMTP_AUTH_PWD: password

If you then invoke the MailServlet at /MailServlet without parameters, it will use defaults. Note in this case, you should change the hard-coded values in the To, From, Subject, Body inside of the MailUtility.sendMailWithEnvValues() method.

Building the Application

mvn install

Running the Application

To run the application, make sure you have VMC installed and that you are logged in successfully for your desired target environment (e.g. http://api.cloudfoundry.com). Then, cd into the directory of this README.md file and make sure the manifest.yml values look correct and then execute:

vmc push --path target/mail-java-1.0.war 
Using manifest file manifest.yml

Creating mail-java... OK

Creating route mail-3ef46.cloudfoundry.com... OK
Binding mail-3ef46.cloudfoundry.com to mail-java... OK
Uploading mail-java... OK
Starting mail-java... OK
Checking mail-java... OK

vmc app mail-java
Using manifest file manifest.yml

mail-java: running
  platform: java_web on java7
  usage: 128M × 1 instance
  urls: mail-3ef46.cloudfoundry.com

Your url will likely be different if you are using the ${random-word} functionality in the manifest.yml file. Invoking that URL should display the index.jsp.

For SendGrid, you should be able to use values like:

smtp host: smtp.sendgrid.net
smtp port: 465
user: SENDGRID_USER
password: SENDGRID_PASSWORD

For MailGun, you should be able to use values from your "Domains" page.

smtp host: smtp.mailgun.org
smtp port: 465
user: postmaster@YOUR_DOMAIN.mailgun.org
password: DOMAIN_PASSWORD