Why does an email bounce?

Last Updated: 11/6/2024     Tags: bounce, email, soft, hard, bounced
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An email could bounce due to a number of reasons. The most common reasons occur due to a subscriber's inbox being full, or their mail server being temporarily unavailable. Some bounces may result in the subscriber being marked as invalid, this is dependent on the type of bounce code passed back to Taguchi.

Currently within V4, bounce codes/reasons are not displayed.

To view a bounce reason within a subscriber profile within V5, simply head to a subscriber profile and locate a bounce event in the activity history. Hover over the bounce icon, a tooltip should appear with the bounce reason and code. A further explanation of bounce codes and reasons is listed below.

Bounce Reason

Bounce reasons and codes

Bounce Code Reason
9801 The response text could not be identified
The bounce reason could not be identified
2810 The recipient's email address is invalid
The email address is not a valid email
3820 The message soft bounced
The recipients mailbox may be temporarily unavailable
4821 The message bounced due to a DNS failure
The email failed to deliver due to a recipient server side issue
3822 The message bounced due to the remote mailbox being over quota
The recipients mailbox is full
2830 No recipient could be determined for the message
The email address is not a valid email
2840 The message failed for unspecified reasons
The email could not be delivered for unknown reasons
1850 The message was blocked by the receiver
The recipients mail server blocked the email from being delivered for an unknown reason
1851 The message was blocked by the receiver as coming from a known spam source
The recipients mail server blocked the email from being delivered as the source has been identified as potential spam
1852 The message was blocked by the receiver as spam
The recipients mail server blocked the email from being delivered as the email has been marked as potential spam
1853 The message was blocked by the receiver because it contained an attachment
The recipient disallows attachments, so the mail server has blocked the email from being delivered
2854 The message was blocked by the receiver because relaying is not allowed
The recipient disallows message relaying, so the mail server has blocked the email from being delivered
9860 The message is an auto-reply/vacation mail
The recipient has an auto-reply or away/vacation message enabled which is causing the message to bounce
2890 The message is an unsubscribe request
The recipient has requested to be unsubscribed through their mail server
9900 The message is a challenge-response probe
The bounce message is a spam-filter challenge response probe
9999 The error from the ISP could not be classified
The response from the mail server could not be revealed

To find out how an email is deemed "invalid", please see What Is An Invalid Email Address?