Emails sent in campaigns can bounce for a number reasons. Common reasons could be \"user over quota\", \"recipients server temporarily unavailable\", \"content rejected\". These bounces are classified into soft bounces and hard bounces. Soft Bounce: When the email has bounced with a reason indicating short term issues with the recipient, they are flagged as soft bounce. These email addresses could later be available in future campaigns. They include reasons like \"Quota exceeded\", \"Too much sessions in a connection\", \"Temporary local problem\", \"Out of Office Auto Reply\" Hard Bounce: When the email has bounced with a reason indicating permanent issues with the recipient, they are flagged as hard bounces. Chances that these emails could later be available for future campaigns is less. The reasons for such bounces could be : \"Mailbox not found\", \"unknown user\", \"mailbox is no longer active\", \"incorrect domain\". Benchmark email recommends cleaning up such emails to improve your statistics for future campaigns. In case the same contact has hard bounces in three consecutive campaigns, Benchmark email automatically flags the contact as a \"Confirmed Bounce\". A \"Confirmed Bounce\" contact will be excluded from your active contact count, and will not be sent any email, if the contact list is selected again. In case a previously bounced email is opened in another campaign before it has been flagged as \"Confirmed Bounce\", the contact\'s bounce counter is reset to zero. This allows bounced emails, to remain in the active contact count and not be flagged as \"Confirmed Bounce\". The \"Confirmed Bounce\" contacts are listed separately in your contact list.