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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 Type Bounce Code [Hidden] Description
Soft 4.2.2 The email account is over quota
Hard 5.0.0 Address does not exist
Hard 5.1.0 Other address status
Hard 5.1.1 Bad destination mailbox address
Hard 5.1.2 Bad destination system address
Hard 5.1.3 Bad destination mailbox address syntax
Hard 5.1.4 Destination mailbox address ambiguous
Hard 5.1.5 Destination mailbox address valid
Hard 5.1.6 Mailbox has moved
Hard 5.1.7 Bad sender\’s mailbox address syntax
Hard 5.1.8 Bad sender’s system address
Soft 5.2.0 Other or undefined mailbox status
Soft 5.2.1 Mailbox disabled, not accepting messages
Soft 5.2.2 Mailbox full
Hard 5.2.3 Message length exceeds administrative limit.
Hard 5.2.4 Mailing list expansion problem
Hard 5.3.0 Other or undefined mail system status
Soft 5.3.1 Mail system full
Hard 5.3.2 System not accepting network messages
Hard 5.3.3 System not capable of selected features
Hard 5.3.4 Message too big for system
Hard 5.4.0 Other or undefined network or routing status
Hard 5.4.1 No answer from host
Hard 5.4.2 Bad connection
Hard 5.4.3 Routing server failure
Hard 5.4.4 Unable to route
Soft 5.4.5 Network congestion
Hard 5.4.6 Routing loop detected
Hard 5.4.7 Delivery time expired
Hard 5.5.0 Other or undefined protocol status
Hard 5.5.1 Invalid command
Hard 5.5.2 Syntax error
Soft 5.5.3 Too many recipients
Hard 5.5.4 Invalid command arguments
Hard 5.5.5 Wrong protocol version
Hard 5.6.0 Other or undefined media error
Hard 5.6.1 Media not supported
Hard 5.6.2 Conversion required and prohibited
Hard 5.6.3 Conversion required but not supported
Hard 5.6.4 Conversion with loss performed
Hard 5.6.5 Conversion failed
Hard 5.7.0 Other or undefined security status
Hard 5.7.1 Delivery not authorized, message refused
Hard 5.7.2 Mailing list expansion restricted
Hard 5.7.3 Security conversion required but not possible
Hard 5.7.4 Security features not supported
Hard 5.7.5 Cryptographic failure
Hard 5.7.6 Cryptographic algorithm not supported
Hard 5.7.7 Message integrity failure
Hard 9.1.1 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).

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