I got something important for you all. In SharePoint 2013 and Office 365 you will face an important issue while working on the SharePoint 2013 platform for sending emails using SharePoint Designers or Nintex.
The issue will be that you will not be able to send emails to SharePoint or Outlook Directory groups as we used to in earlier versions of SharePoint. I found this question unanswered on some blogs so I thought of doing some R & D.
If you use SPD to create a workflow and select the platform type as 2010 it will work but not with 2013. So what you have to so is, the DL you want to send email to, add them to the permission level of the site. We never used to do this in earlier versions of SharePoint, but now give them read access to the site and configure the workflow.
It will work. Try this and let me know for any feedback or concerns.