When you add the Email Invalid Cause to display as a Column to any of your Deliverability Smartlists, you will see a code value*, and potentially a suffix as well, to help you understand the reason for a Hard Bounce. Soft Bounce reasons can't be viewed through a Smart List report, only one at a time in a lead's activity log.
- Codes in the 400 range are generally Soft Bounces
- Codes in the 500 range are generally Hard Bounces
*Mail server administrators can create custom messages that accompany bounce codes
Traditional Bounce Codes
Mail accepted by receiving network
<domain> Service not available, closing transmission channel
Requested mail action not taken: mailbox unavailable (e.g., mailbox busy)
Requested action aborted: error in processing
Requested action not taken: insufficient system storage
The server could not recognize the command due to a syntax error.
A syntax error was encountered in command arguments.
This command is not implemented.
The server has encountered a bad sequence of commands.
A command parameter is not implemented.
User’s mailbox was unavailable (such as not found)
The recipient is not local to the server.
The action was aborted due to exceeded storage allocation.
The command was aborted because the mailbox name is invalid.
The transaction failed for some unstated reason.
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Enhanced Bounce Codes
If a suffix appears after one of the codes above, it is an enhanced Bounce code
*Mail server administrators can crate custom messages that accompany bounce codes
Address does not exist
Other address status
Bad destination mailbox address
Bad destination system address
Bad destination mailbox address syntax
Destination mailbox address ambiguous
Destination mailbox address valid
Mailbox has moved
Bad sender’s mailbox address syntax
Bad sender’s system address
Other or undefined mailbox status
Mailbox disabled, not accepting messages
Message length exceeds administrative limit.
Mailing list expansion problem
Other or undefined mail system status
Mail system full
System not accepting network messages
System not capable of selected features
Message too big for system
Other or undefined network or routing status
No answer from host
Routing server failure
Unable to route
Routing loop detected
Delivery time expired
Other or undefined protocol status
Too many recipients
Invalid command arguments
Wrong protocol version
Other or undefined media error
Media not supported
Conversion required and prohibited
Conversion required but not supported
Conversion with loss performed
Other or undefined security status
Delivery not authorized, message refused
Mailing list expansion prohibited
Security conversion required but not possible
Security features not supported
Cryptographic algorithm not supported
Message integrity failure