Hard bounce:

A hard bounce is a permanently failed address. This means that the address is not valid or it no longer exists. Hard bounces are removed from the active subscriber list and quarantined in the Manage Bounces section. You are able to edit these addresses if need be. For instance, if you find an address that has been spelled wrong like joe@alo.com and you know it should be joe@aol.com, you are able to individually edit that address.

It is not recommended to delete addresses that are Hard Bounces.  Each time you upload a new file of subscribers we will automatically scrub that file against your Hard Bounces to ensure that you are not continually trying to mail to bad addresses.

Once you have edited the address and saved the changes, that address will be placed back into your active subscriber list. If the address hard bounces again, it will be placed back in the Manage Bounces section.