When an email message is considered permanently undeliverable, this is considered a “hard bounce.” Emails become undeliverable when the receiving address is invalid. In this case, the email client (e.g., Gmail, AOL, Yahoo, etc.) will not try to redeliver the message again. To maintain a high delivery rate for all of our customers, as well as to save you the manual effort of keeping your lists clean, AssociationSphere will automatically unsubscribe all of the hard bounced emails (You can view the reason for the unsubscribe on the All Recipients screen.) To avoid hard bounces, make sure you are only sending to the legitimate email addresses of people who have given you permission to contact them.