Send Email -Workflow

Scott, 

I tried using message gateway service to send out an email, in my custom workflow process step, but keep getting the error, a NPE, i have keyed in smtp port and username etc in CQ mail service configuration in system console. I see people posting issues on the same, please help me with this.

Code:

@Reference
private MessageGatewayService messageGatewayService;

     ArrayList<InternetAddress> emailRecipients = new ArrayList<InternetAddress>();

public void execute(WorkItem item, WorkflowSession session,

    MetaDataMap metaData) throws WorkflowException {

HtmlEmail email = new HtmlEmail();

      emailRecipients.add(new InternetAddress("email") );
      email.setTo( emailRecipients );
      email.setSubject( "This is subject");
      email.setHtmlMsg( "Email testing");

Error:

messageGatewayService : com.day.cq.mailer.impl.CqMailingService@c14701
messageGateway : null
Fatal error while sending email in workflowjava.lang.NullPointerException

If OOTB does not address your needs -- then yes - you are correct - a custom workflow step is the way to go. Remember that a custom workflow step is just like any other OSGi bundle which is Java. So there is not much you cannot accomplish. If you want to get CQ users for you custom workflow step -- you can use the CQ com.day.cq.security.UserManager. API. To learn how to work with this API, see http://scottsdigitalcommunity.blogspot.ca/2013/07/using-ajax-requests-to-display-adobe-cq.html. 

No Scott, I am trying to create a workflow step mocking the Send Email functionality, Since not all my requirements might be met by OOTB component. 

Justin, 

I wonder if this has been missed out in Documentation , but if one needs to send out email from AEM, on start up -Djava.net.preferIPv4Stack=true needs to be added.

Wish it was known earlier, Would be helpful for others trying to crack this issue. Thanks for help and patience ,