There are 2 types of bounces associated with CG sends. Soft and Hard bounces. 


A soft bounce normally happens when the receiving Mail Server is temporarily unable to receive the email.  There are several reasons why this would happen. The following are reasons for soft bounces.

  • A server is unavailable or it’s down
  • The server is overloaded
  • The recipient’s mailbox is full
  • Your message size is too big


In this case CG tried to deliver the message again at a later point in time. This is why soft bounces may take a few days until they show up in the Bounce section of the Data Transport Report.


A hard bounce is more permanent. A hard bounce removes the subscriber from the list. There are several reasons why an email would hard bounce. The main characteristic though, is that it is a permanent rejection.   Below is a list of the most bounce codes:


Bounce code

Bounce type

Description

5.0.0 Hard Address does not exist
5.1.0 Hard Other address status
5.1.1 Hard Bad destination mailbox address
5.1.2 Hard Bad destination system address
5.1.3 Hard Bad destination mailbox address syntax
5.1.4 Hard Destination mailbox address ambiguous
5.1.5 Hard Destination mailbox address valid
5.1.6 Hard Mailbox has moved
5.1.7 Hard Bad sender\’s mailbox address syntax
5.1.8 Hard Bad sender’s system address
5.2.0 Soft Other or undefined mailbox status
5.2.1 Soft Mailbox disabled, not accepting messages
5.2.2 Soft Mailbox full
5.2.3 Hard Message length exceeds administrative limit.
5.2.4 Hard Mailing list expansion problem
5.3.0 Hard Other or undefined mail system status
5.3.1 Soft Mail system full
5.3.2 Hard System not accepting network messages
5.3.3 Hard System not capable of selected features
5.3.4 Hard Message too big for system
5.4.0 Hard Other or undefined network or routing status
5.4.1 Hard No answer from host
5.4.2 Hard Bad connection
5.4.3 Hard Routing server failure
5.4.4 Hard Unable to route
5.4.5 Soft Network congestion
5.4.6 Hard Routing loop detected
5.4.7 Hard Delivery time expired
5.5.0 Hard Other or undefined protocol status
5.5.1 Hard Invalid command
5.5.2 Hard Syntax error
5.5.3 Soft Too many recipients
5.5.4 Hard Invalid command arguments
5.5.5 Hard Wrong protocol version
5.6.0 Hard Other or undefined media error
5.6.1 Hard Media not supported
5.6.2 Hard Conversion required and prohibited
5.6.3 Hard Conversion required but not supported
5.6.4 Hard Conversion with loss performed
5.6.5 Hard Conversion failed
5.7.0 Hard Other or undefined security status
5.7.1 Hard Delivery not authorized, message refused
5.7.2 Hard Mailing list expansion prohibited
5.7.3 Hard Security conversion required but not possible
5.7.4 Hard Security features not supported
5.7.5 Hard Cryptographic failure
5.7.6 Hard Cryptographic algorithm not supported
5.7.7 Hard Message integrity failure
9.1.1 Hard Hard bounce with no bounce code found. It could be an invalid email or rejected email from your mail server (such as from a sending limit).