The message cannot be sent to all selected recipients. 

When running a workflow / process in Microsoft CRM, you receive a message that looks like this:

The e-mail address for one or more recipients is either blank or not a valid e-mail address

The Cause

This error message is a little misleading as it points to an email address problem. As the title of the error suggests, the problem could be from:

1. A blank email address.

2. An email address with an error, such as a “.” at the end of it: email@addresss.com.

3. The more likely one is that the contact or account record associated with the flow has a setting to 

E-mail Do Not Allow.

This setting will prevent any workflows in CRM from running and sending email messages.

The Solution

The fix is easy… just change the setting back to allow. Then save the associated record.

You then need to restart the stalled process or workflow.