There are a number of reasons why certain emails are returned as "undeliverable." Sometimes it means that the recipient is no longer with the company and his or her email account has been deleted. Other times, the company's email system may have encountered a temporary error.

Email filters and firewalls can also cause problems. Some email accounts only allow emails from people who are in the user's address book. With a very small percentage of companies, an email campaign will simply not be effective. However, BuzzBuilder has been designed to work with the vast majority of email accounts and we have the highest possible rate of delivery.