If you find that email addresses are not set in a client mailshot, you need to ensure that the primary email address in the client record is set. To check this, please follow the below steps:
Click Clients and then select the Client.
Click the Phones tab.
Make sure there are valid eMail addresses listed - if not add one.
Click the Details tab and then click the pencil icon next to the Primary Email field.
Select the email address from the list shown and click the tick icon.