Introduction
What is an email bounce? Understand and manage these errors to improve your deliverability
In the world of email marketing, the deliverability and the bounce rate are key factors for success. It is not enough to simply send an email: it must also arrive in your recipient's inbox.
A negative delivery return, or bounced email, signifies a delivery failure. In other words, your email could not be delivered to its recipient. For technical or structural reasons, the recipient's server returns an error message to you. Understanding the nature of these errors, knowing how to interpret them, and managing them effectively is essential to protect your sender reputation and maximize the rate of deliverability of your campaigns.
What is a bounced email, cancelled email, or error email in emailing?
This happens when an email you sent is returned by the recipient's mail server. This bounce can be immediate or deferred, depending on the reason for the rejection. The bounce often contains an error code and a message explaining the reason for the rejection.
There are two main types of rebounds:
Hard bounces, bounced emails permanent
It occurs when an email is permanently bounced back. It is a delivery failure irreversible. The most frequent causes are:
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- The email address is invalid or misspelled
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- The address no longer exists or never existed
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- The recipient's domain name is incorrect or no longer active
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- The recipient's server permanently rejected the email
Examples:
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501 Syntax error in parameters or arguments Invalid parameter (e.g., improperly formatted email address).
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507 Insufficient storage The server does not understand the command.
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503 Bad sequence of commands SMTP commands were sent in the wrong order.
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504 Command parameter not implemented Parameter not recognized by the server.
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550 Requested action not taken: mailbox unavailable The recipient's email address is invalid or does not exist.
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551 User not local; please try The address is not handled by this server (incorrect DNS configuration or redirection).
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552 Requested mail action aborted: exceeded storage allocation The recipient's mailbox is full.
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553 Requested action not taken: mailbox name not allowed Invalid or forbidden email address.
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554 Transaction failed / Message rejected Message refused, often for reasons of content, blacklist, spam, or IP reputation.
Permanent rebounds must be deleted immediately from your database, continuing to send emails to these addresses severely damages your sender reputation. A high bounce rate can lead to blocks from email service providers (Gmail, Outlook, Yahoo...).
2. Soft bounces, temporary email bounces
It occurs when the delivery failure is temporary. The message arrived at the recipient's server, but could not be delivered to the inbox for a temporary reason. Common causes include:
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- The recipient's inbox is full
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- The server is temporarily unavailable
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- The message is too large
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- A temporary filter rule is blocking the email
Examples:
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421 Service not available The destination server is temporarily unavailable (overload, maintenance...).
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450 Requested mail action not taken: mailbox unavailable The inbox is temporarily inaccessible (e.g., mailbox full).
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451 Requested action aborted: local error in processing Internal server error. The email could not be processed.
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452 Too many recipients / insufficient system storage Too many emails sent or server storage full.
In this case, the sender's server will generally try to Try sending again for a defined period (24 to 72 hours depending on the systems). If the failure persists, the temporary rebound can end up being converted into a permanent one.
Why is it crucial to manage these negative reviews?
1. Protect your shipper reputation
Email providers monitor bounce rates. A high rate can make you look like a spammer. This can lead to:
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- A drop in deliverability
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- A spam ranking
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- A temporary or permanent blockage of your shipments
2. Improve your campaign statistics
By removing invalid addresses, you improve the your database quality, which translates to better open and click rates and fewer email bounces. This allows you to focus your efforts on truly active contacts.
3. Reduce costs
If you use a paid email routing tool like the one we offer, sending emails to invalid addresses represents an unnecessary cost. Avoiding errors also means optimizing your budget.
Best practices for limiting errors
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- Validate email addresses during registration (double opt-in, captchas, syntax check).
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- Regularly clean your database, by removing hard bounces and monitoring persistent soft bounces.
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- Use an authenticated domain name (SPF, DKIM, DMARC) to strengthen the trust of destination servers.
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- Avoid untargeted mass mailings or to purchased bases and follow them best practices.
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- Monitor your campaign reports to quickly detect anomalies.
In a nutshell
Delivery failures email, email bounces is a key indicator of the health of your email marketing campaigns. By understanding the difference between difficult and tender, and by implementing proactive management, you improve your deliverability, protect your sender reputation and increase the overall effectiveness of your campaigns.
At Efidem, we are making available to you on Snapshoot advanced tracking tools and a support customized to help you better manage your email bounces, analyze, clean, and segment your mailing lists. Contact us to optimize your email campaigns and SMS !
Thanks for reading!
