This page explains "To" in bulk email delivery.
Specifications
Contacts, shown by tags or in lists, with the following attributes can be set as recipients.
- Email address in "Email1"
- Details (name, importance, company information, Email1) are not set as private
Exceptions to those above
- Contacts with multiple email addresses
・Only the most recently registered email will be included." - Recipients included are in the undeliverable list
・If the delivery status is "Unknown user", "Unknown host", "Rejected", or "Unidentified error", the contact will be automatically added to the undeliverable list and excluded from future emails. - When doing one-to-one mails, the sender email address (contact owner) isn't the registered address.
- There are recipients on the unsubscribed or blocked lists.