What is the difference between hard and soft bounces?

When you’re analyzing the results of your transactional emails it is important to identify your percentage of Soft and Hard bounces. Let’s start from the beginning by learning their concept and the difference between them.

Soft Bounces

This type of bounces are caused due to errors or non-permanent situations that can be reversed over time.

When Doppler Relay receives a Soft Bounce we retry some times with intervals of time based on each ISP until its successful delivered before definitively called it a hard bounce.

Here are some reasons why a you can have a soft bounce:

Email Rejected: The sent Email returns to our platform. In most cases, this happens because the user’s mailbox is full, causing the email not to reach the destination.

Invalid host: This type of bounce occurs when the destination server no longer exists.

MX Record Not Found: Registry is not found in DNS. In these cases, it is possible that the domain doesn’t exist or that the DNS is not updated.

Time out: Occurs when the connection has taken more than 60 seconds to be made. When this happens, try again later.

– Server Rejected: The destination server rejects the SMTP connection.

– Transaction Error: The connection can not be established or the destination server does not allow the connection for some reason.

The last two cases mentioned appear to be technically complicated, but essentially what happens is that the connection attempting to perform Doppler Relay is not accepted or is not answered by the destination server.

Hard Bounces

Hard type bounces are more severe than the Soft, hence the meaning of their names. They happen when Doppler Relay obtains a definite answer from the destination server, indicating that that Email can not and can never be sent to that destination box.

The response will be “Email Rejected” or “Invalid Email Format”. These types of bounces usually happen due to:

– One of the contact addresses to which the sending was made is invalid, either because it has been unsubscribed, because it was erroneously typed in the List or because it has never existed.

– The domain name does not exist.

– The recipient’s server has completely blocked delivery.

– The server is blocking the Email because it contains an attachment.

– The receiving mail account is blocking Emails from your server.

– The receiving server considers spammer to your domain.

– The server considers the content of the message to be Spam.

In all these cases, the application will not attempt to forward the Emails and automatically consider them as Hard Bounces.

How to avoid Soft and Hard bounces?

The best way to reduce the number of bounces is by following some best practices for delivering key email. This includes the following:

Maintain a good list of subscribers

Delete regularly from your list of invalid emails. High bounces rates can affect the reputation of your business as a sender, so keeping your lists clean will help you achieve higher delivery rates.

Use double opt-in

Send a confirmation email when users subscribe to your list. This way you can make sure that the user’s email is not only valid, but in fact they want to receive your email messages.

Monitor the delivery of your Transactional Emails

Never lose sight of the percentage of deliverability of your transactional shipments, if you detect a drop in your percentage you will have a good hint to check your hard bounces.


Was this article helpful?
Help us improve our assistance by rating it
1 Star2 Stars3 Stars4 Stars5 Stars
Loading...

Leave a Reply

Your email address will not be published. Required fields are marked *

I accept Doppler's Privacy Policy.



Doppler informs you that the personal data that you provide to us when completing this form will be treated by Doppler LLC as responsible for this web.

Purpose: To allow you to make comments in our help center.

Legitimation: Consent of the applicant.

Recipients: Your data will be saved by Doppler and Digital Ocean as hosting company.

Additional information: In the Doppler Privacy Policy you’ll find additional information about the collection and use of your personal information by Doppler, including information on access, conservation, rectification, deletion, security, cross-border data transfers and other issues.