It’s long been an issue/feature with SharePoint Designer 2013 Workflows (yes, some people still use that today), that you cannot send an e-mail to an external email or a shared mailbox. SharePoint Designer 2013 Workflow can only send emails to organization users and a shared mailbox is not a user. So even if you want to send an email to some internal distributionlist or mailbox, you are not able to do that, using 2013 workflow.

If you try sending an email to an external or shared mailbox you will most likely end up with an error like this: “BadRequest to /_vti_bin/client.svc/sp.utilities.utility.SendEmail”.

So to do it, you have to get your “SharePoint Designer 2013 Workflow” to start a “SharePoint Designer 2010 Workflow”. the SPD2010 Workflows only task is to send that email to the shared mailbox.

SharePoint 2010 Site Workflow

Step 1: Create a SPD 2010 Site Workflow

Step 2: Create 3 Initiation form parameters

Parameter definitions:

NAME	INFORMATION TYPE
emailbody	Multiple lines of text
recipient	Single line of text
subject	Single line of text

Step 3: Create a “Send Email” action

Step 4: Input the parameters in the “To”, “Subject” and “Body” areas of the email

Step 5: Publish it

SharePoint 2013 Workflow

Now, the task is to create or edit your SPD2013 Workflow to start the SPD2010 Workflow with the correct parameters.

Step 1: Define 3 variables for use when starting the 2010 Workflow in the next step

Parameter definitions:

NAME	VARIABLE TYPE
Recipient	String
mailsubject	String
EmailBody	String

Step 2: Create “Start a Site Workflow” action
Step 3: Select the “send email” workflow from the list

Step 4: Match the 3 parameters with the 3 variables

NOTE: The recipient parametervalue should be type = String.

You should end up with a result that looks like this:

Now, each time your SPD2013 Workflow runs, it will start the SPD2010 Workflow to send out the email. This is, so far, the only way I’ve found that a email to an external email or shared email can be sent from a SharePoint Designer Workflow.