Want to know why do you get a Bounce Mail or a Bounce Notification?

Bounce Notification – Types, what causes them, how to set up and how it works?

November 15, 2017

We all have received bounced emails in our mailboxes now or then. When we try to send email to someone, we sometimes suddenly get a message stating that this mail has not been delivered. This message is called Bounce Mail or Bounce Notification.

bounce notification email

Curious to know how to read those complexly written automated bounce notification emails, or what causes them, how to set up them, how they work and before all that – what are they? Read on and understand it all.


What is a Bounce Notification?


Bounce Notification is an automated message and sent from an email system. It is used to inform the sender that his message is not delivered to the intended recipient successfully. The notification contains non-delivery report of a failed email, failed delivery status, an error message or what error might have been occurred and the non-delivery notification. The email, that contains these messages about a failed email, is called bounces or bounce notification. Email bounces must be closely monitored and managed.


Reasons for a bounce notification


Reasons for getting an email bounce notification can be many; starting from email address has been changed, the domain has been changed, the mailbox is full etc. We can categorize the email bounces into two main categories –


  • Hard Bounces – A hard bounce of an email is the bounce caused by permanent non-deliverable conditions of emails such as the recipient’s email address is missing or invalid. Another reason for a hard bounce to occur can also be non-existence of the recipient’s domain, unknown recipient, error in typing the recipient’s email address, blocking of your mail server by the recipient’s mail server, or any kind of network glitch at the recipient’s end.


  • Soft Bounces – If an email message is able to find the recipient’s mail server and recognize the address, but it is not delivered to the recipient’s inbox and bounced back before delivery. This is a soft bounce. The reasons can be many like recipient’s inbox is full, the recipient’s mail server is down for some reason, the mailbox is abandoned by the user. After some attempts at delivery and soft bounces, it is transformed into a hard bounce.

hard bounce soft bounce

So, we can list some reasons for which bounce notifications can arrive on the failure of an email delivery:


  1. Unknown user: This can be a reason when the mailbox exists no longer, mail provider is shut down or the email address is not valid or may be a portion of the email address is not valid.
  2. Full Mailbox: Each mailbox has a limit to store emails at a time and if that limit exceeds, the recipient’s server will reject any incoming email and it will be shown as a bounce notification in sender’s email box.
  3. Too Large Message: This happens rarely but still this is a cause of getting a bounce notification. The size of your email is defined by your service provider as well as the recipient’s service provider. Meaning of this bounce is you have written a mail which exceeds that defined size, which includes the header, text message, attachments, etc. In this case, too, the recipient’s server will reject the incoming mail for being too large than their defined size to accept.
  4. Did not Find Domain: This typically means that the domain your mail is intended to, does not exist or shut down.

These are main causes of getting an email bounce notification. Other causes include – mail is trapped in a routing loop, connection timed out or network error, domain’s internal issues like switching hosts, blocking of a certain type of IP addresses from recipient’s mail server, unknown or undefined reasons etc.


How does the bounce notification work?


To understand the functionality of bounce notification, we need to understand the email flow first.

email flow
Image Source: https://blogs.technet.microsoft.com/ptsblog/2013/08/13/office-365-mail-flow-troubleshooter/

Here in the flowchart, we can see the journey of the email along the components. After passing through all the components, there is a handshaking stage. The SMTP server of the intended recipient takes a big role here, it helps to recognize the sender’s domain and make a contact with the receiving server. The recipient server goes through the message and checks the parameters mentioned above to give a green signal to the mail. If any of the parameters is missing, wrong or unknown, the recipient’s server rejects the email. Now the mail is sent back to the sender’s server and bounce notification is sent to the sender’s inbox.


How to read the bounce notification emails?


Bounce messages have specific formats and it is predefined by the mail server. Bounce notification can be a MIME multipart report message. It comprises three parts –

  1. An explanation in human-readable format.
  2. Delivery status which can be parsed by a machine. This includes a “name: type, value” parameter.
  3. The original notification message indicating the possible causes.


How to read bounce notification
Image Source: https://en.wikipedia.org/wiki/Bounce_message#Terminology


How to set up bounce notification?


  • In Pepipost, to get bounce notification you need to navigate to Settings -> Customize -> Bounce Notification -> View Settings.


  • First, you need to create and Custom Envelop. To create a Custom Envelop you need to go to Domain Management -> Settings and create custom envelop to get bounce notifications.


  • With this, the bounce forwarding within your account is enabled. Now each time, when a bounce will appear, the system will automatically notify you. It will forward a bounce notification on the email address, which you have set for bounce forwarding.


To handle these notifications, you need to configure your app to receive bounces. For that, Real-time Event Notification API has to be enabled in the application. Also, list of email bounces can be edited and retrieved through Web APIs of your service provider. Hard and Soft Bounces can be handled differently and it can be handled through your account or APIs provided by your service provider.


Additional benefit of setting up these notifications is – it will also notify about clicks, opens or anything that happened to the emails. So, you can easily calculate the response rate and improve your mailing campaign’s strategy accordingly.


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Dibya Prakash Sahoo|The Business Guy