Sometimes you'll create a list to email to and find no addresses have been added. Here are some troubleshooting tips to get your list back to the right size.
Email Opt out is checked - If you have a smaller list and end up with no one on it, check that the Leads/Contacts haven’t unsubscribed. If the Email Opt out box is checked, VerticalResponse won’t pull the email address into the list.
Custom Field - if email addresses are being stored in a custom field, our system won’t see them as an email address and won’t pull them over. Our system will map email addresses from Salesforce to the email field in VR. In order to send emails you’ll need to use the Salesforce default email field.