When an email is rejected by a subscribers email server, it's referred to as a bounce. Based on the reason for the rejection, there are different types of bounces, that can be categorized as either hard - or soft.
If an email address bounces, you can always find out why in the detailed report, The report also tells you whether the bounce is soft or hard.
A hard bounce indicates that the rejection is permanent. This is what happens if the recipients email address does not exist, or the email cannot be delivered.
A hard bounce will deactivate the email adress immediately, and so our system will learn that an email will never get delivered to that specific email adress.
A soft bounce indicates a temporary delivery issue, such as a full mail box, accordingly our system will try to send the email again.
A soft bounce will not deactivate the email address, unless that specific email adress gets three soft bounces in a row.