A bounce is a message which is returned to our server as undeliverable. Bounces occur, for example, when someone changes their email address without unsubscribing from your list. Or bounces occur when someone abandons an email address and the account fills up to its limit with unread mail. And some bounces occur because of defective SpamFiltering? on recipient servers.
Bounce handling for newsletter lists
Addresses are removed from newsletter lists automatically if they bounce on three successive mailings. Thus no bounce removals will be reported on new lists until you have done three mailings. Then as you launch the fourth mailing, addresses which bounced on the three previous mailings are first removed and reported to you on that day's DailyReport.
Bounce handling for discussion lists
Addresses are removed from discussion lists automatically if they bounce on three successive days. Removed addresses are reported in the DailyReport.