Is it possible to send email to Distribution Group using SharePoint Designer Workflow 2013? I have been trying to send email but it does not resolve to a proper name in SharePoint Designer 2013.
not possible, as it is by design in SharePoint 2013 Designer workflows, if you want to use this functionality you have to use the SharePoint 2010 workflows. SharePoint is attempting to validate the users within the Distribution Group using REST services validation. Microsoft remove sending email to DL or security groups or external users in SP 2013 and up.
SharePoint 2013 workflows can only send emails to organization users.
Their is workaround Microsoft folks mentioned on his blog: SharePoint 2013 – Unable to send emails to external email addresses (SharePoint 2013 workflows)
Also you up vote and put pressure on MSFT bring back this functionality over here: SharePoint 2013 workflow email to distribution list