Emails that bounce are generally a result of a nonexistent or otherwise invalid email address. Most are permanently marked as bounced in your account and cannot be mailed to in the future. There may also be temporary delivery issues, a full mailbox or technical issues with the receiving server, leading to delivery delays or a bounced email address. Most of these email address will remain mailable in your account. Lastly there may be rare cases where a block from a particular domain causes delivery rejection and leads to a bounce.
If you feel emails are bounced in error we can debounce your account to set these addresses as mailable. However, we can only do this a total of three times for the lifetime of your account. If there are ongoing delivery issues related to a particular domain or email address, our delivery team can work with you directly.
You'll find more information on bounces and VerticalResponse bounce handling in the following documents. http://www.verticalresponse.com/sites/www.verticalresponse.com/files/4-11_debouncing_bounced_emails.pdfhttp://www.verticalresponse.com/sites/www.verticalresponse.com/files/bounce_guide.pdf