Soft Bounce: Soft bounces basically mean the email was sent to the server, processed, but for some reason was returned to us. Common reasons include: "user over quota," and "server temporarily unavailable."
****NOTE: If you're receiving an email returned into your own email account noting that someone is on vacation or is out of the office, that address is not necessarily getting noted as a soft bounce in Total Send.
Most of your recipients' servers should be set up to NOT report to us that the address bounced. If they did, your recipient might want to let their IT group know that they are getting taken off important mailing lists while they are on vacation.
Hard Bounce: A hard bounce basically means we sent your email, and the recipient's server outright rejected it. Common reasons include: "Account does not exist," and "domain does not exist."
Our systems are 99.9% accurate at determining soft/hard bounces. However very occasionally a false classification can occur. This only happens as a result of the rarest of server responses, when our servers misinterpret an error sent from the recipients server.