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Understanding Different Email Bounce Codes

A contact gets marked as bounced when an automation email or email campaign gets rejected by their receiving email server. A rejection here means that the email address if not accessible at that time or it is invalid.

Generally, there are two types of bounces tracked:

  1. Hard Bounces
  2. Soft Bounces

A hard bounce means a permanent rejection or failure. When a hard bounce is received, we immediately mark the contact as “Bounced” and that contact no longer receives any automation or campaign email from us.

A soft bounce means a temporary rejection of failure. 

A number of factors lead to a soft bounce; some of these are:

  • Overloaded server
  • The recipient has a full mailbox
  • Big message size
  • The server is down or not available

After a contact soft bounces, we do not mark it as bounced immediately; instead, we mark it as “ bounced” after it happens three times in three separate campaigns. After this, the contact no longer receives messages from you. 

In your campaign and automation email report, we mention the details of contact bounces such as the bounce code, date of the bounce, type of bounce and its description.

Note: We do not mention bounce codes explicitly on your report page. If you want to know the bounce code, you will need to connect with the customer support team to get the same. Bounce codes are the ones that our servers get from the mail servers of the recipients. However, it is possible that these codes do not always reflect the true nature of the bounce.

Refer: Techniques to prevent bounce rates inside Aritic PinPoint

Below mentioned is a list of bounce codes that we support and use: 

Bounce TypeBounce Code [Hidden]Description
Soft4.2.2The email account is over quota
Hard5.0.0Address does not exist
Hard5.1.0Other address status
Hard5.1.1Bad destination mailbox address
Hard5.1.2Bad destination system address
Hard5.1.3Bad destination mailbox address syntax
Hard5.1.4Destination mailbox address ambiguous
Hard5.1.5Destination mailbox address valid
Hard5.1.6Mailbox has moved
Hard5.1.7Bad sender\’s mailbox address syntax
Hard5.1.8Bad sender’s system address
Soft5.2.0Other or undefined mailbox status
Soft5.2.1Mailbox disabled, not accepting messages
Soft5.2.2Mailbox full
Hard5.2.3Message length exceeds administrative limit.
Hard5.2.4Mailing list expansion problem
Hard5.3.0Other or undefined mail system status
Soft5.3.1Mail system full
Hard5.3.2System not accepting network messages
Hard5.3.3System not capable of selected features
Hard5.3.4Message too big for system
Hard5.4.0Other or undefined network or routing status
Hard5.4.1No answer from host
Hard5.4.2Bad connection
Hard5.4.3Routing server failure
Hard5.4.4Unable to route
Soft5.4.5Network congestion
Hard5.4.6Routing loop detected
Hard5.4.7Delivery time expired
Hard5.5.0Other or undefined protocol status
Hard5.5.1Invalid command
Hard5.5.2Syntax error
Soft5.5.3Too many recipients
Hard5.5.4Invalid command arguments
Hard5.5.5Wrong protocol version
Hard5.6.0Other or undefined media error
Hard5.6.1Media not supported
Hard5.6.2Conversion required and prohibited
Hard5.6.3Conversion required but not supported
Hard5.6.4Conversion with loss performed
Hard5.6.5Conversion failed
Hard5.7.0Other or undefined security status
Hard5.7.1Delivery not authorized, message refused
Hard5.7.2Mailing list expansion restricted
Hard5.7.3Security conversion required but not possible
Hard5.7.4Security features not supported
Hard5.7.5Cryptographic failure
Hard5.7.6Cryptographic algorithm not supported
Hard5.7.7Message integrity failure
Hard9.1.1Hard 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).

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