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Common email bounces and how to deal with them

Bounced emails are unavoidable in email marketing, what matters is how you deal with them. In this article we look at the different bounce categories and what actions you should take if you get them.
 
Hard and soft bounces
 
To keep your subscriber list up to date and to get the best results from your email campaigns, we recommend you clean the bounced emails from your database following each campaign you send. How you will manage these will depend on the type of bounce you have.
 
There are two categories of email bounces – hard and soft. A hard bounce will indicate a permanent issue with the recipients email address (e.g. the email address doesn’t exist any more). A soft bounce can indicate a temporary or resolvable issue with the email address (e.g. the recipients mailbox is full).
 
Bounce messages
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4.4.1 – host not responding category:  Soft bounce.
Issue: The recipients email host is not responding. This could be due to a temporary issue with their network.
Action required: We recommend resending the email as it’s possible the issue is transient. If the email continues to bounce back you should then consider contacting the recipient to update their contact information or remove their email address from your database.
 
5.0.0 – undefined status category: Hard and soft bounces
 
Issue: This type of bounce is generic and can include bad mailbox, inactive mailbox, policy related, routing errors, etc.
Action required: You will need to delve deeper into the bounce message to identify the reason the email bounced. Generally speaking the bounce reason will appear somewhere within the full bounce message, as highlighted in the example below:
“Status: 5.0.0 (undefined status) Remote-MTA: dns;domainname.com (12.123.1.123) Diagnostic-Code: smtp;550 unknown user X-PowerMTA-BounceCategory: bad-mailbox“Once you’ve identified the reason, you should then take action appropriate to that bounce type.
 
5.1.1 – user unknown category: Hard bounce
Issue: This message indicates the email account doesn’t exist at the organisation or domain the message was sent to. 
Action required: As this is a hard bounce you should remove the bounced email address from your database. We would then recommend contacting the recipient or organisation to confirm the correct email address or get up to date contact details.
 
5.1.2 – no such domain category: Hard bounce
 
Issue: This message indicates the domain the email was sent is incorrect or does not exist. 
Action required: As this is a hard bounce you should remove the bounced email address from your database. We would then recommend contacting the recipient to confirm the correct email address so you can update your database.
 
5.2.2 – mailbox full category: Soft bounce
 
Issue: This bounce message indicates the recipient’s mailbox has reached its storage limit so your email was unable to be delivered. This could simply be because the recipient has been out of the office and has received a lot of emails or could possibly indicate the account is no longer in use but has not been deactivated so emails are not being read and deleted.
Action required: As this is a soft bounce we would recommend trying to send to this email address again. If the email address continuously bounces back you should consider contacting the subscriber to confirm if it’s still the correct address to send to or removing the email address from your database.
 
5.7.1 – delivery not authorised category: Soft bounce
Issue: This bounce message indicates the recipient may have mailbox restrictions which mean the delivery of your email is not permitted. For example their mailbox may be set up so it only accepts emails from senders on a safe senders list.
Action required: As this is a permissions issue we recommend contacting the recipient to request they add you to their accepted senders list. Once you have been added to their permissions list you should be able to successfully deliver emails into their inbox.