If you are sending an email blast to the same recipients multiple times in your org, you can select those recipients in your org and create views in Salesforce. And the same view can be used every time when you send an email blast using the PK4Connect app.
Create View in Salesforce
Select the object to create a view, create the view by selecting the recipients in the view. Make sure that all the recipients you have selected have an email ID in it. Save the view and use it for sending mass emails.
Once you have created the view, use it for sending mass emails, click here to know more about sending emails using the PK4Connect app.