The “bounces” are the error notifications returned from inexistent addresses. In 95% of the cases, these are addresses or domains that do not exist anymore. In 5% of the cases, the address was written incorrectly.
We can define the bounces in two categories: "Hard Bounce" and “Soft Bounce”. In the first case the address is directly added to the bounces list. The address does not exist anymore; a further attempt would have no effect.
In the second case the address returns a temp error notification, for example, for a full mailbox. The delivery system will make several attempts to deliver the newsletter during the next 48 hours. On our emailing platform, Mailpro™, the bounces are treated at regular intervals. As the system sends your emailing campaign several times prior to reporting an address as invalid, it might take up to 48 hours to mark an address as a “bounce”.
For much more information about hard and soft bounce and how we treate them with mailpro, read this!