Bounce is generally speaking any email that hasn’t been delivered. There are two categories of the “bounce,” soft bounce and hard bounce.
A soft bounce is an email that has been processed by a server, but for some reason it returned to a sender. There are many reasons why the soft bounce could occur. For example, an email massage has bounced because the recipient’s mailbox was full, the message was too large or the server was busy. If the email soft-bounces three times with traceable activity, it will be automatically converted into a hard bounce.
A hard bounce is any permanently undeliverable email message that got back to the sender. The hard bounce occurs when the address or domain name doesn’t exist and when your server was blocked by the recipient’s server.
You can use several methods to avoid soft or hard bounces. Please go to our post – List Verify – to learn more!
http://www.velocitymarketingsoftware.com/blog/index.php/2012/07/list-verify-service/