Understanding Undeliverable Emails: Hard Bounce vs. Soft Bounce

“Bounce” is supposed to be a fun word. It makes me think of being a kid again. Bouncing my basketball inside the house and driving my mother crazy. It may remind you of your kids bouncing off the walls, especially with the candy and sweets season in full swing!

Unfortunately, in the email world, bounce isn’t a fun word at all. No client or customer wants to hear that their email “bounced”! This means that the email did not reach its intended destination for one reason or another.

The definition of the word “bounce” as related to email, according to Wikipedia, is an email returned to its sender after failing to reach its destination.

A bounced email is sent back to its origination as “Undeliverable” by the receiving ESP (Email Service Provider). An example of an ESP would be Gmail, Yahoo, or AOL. When the email is returned to you, it is coded/flagged as either a “Soft Bounce” or a “Hard Bounce”.

Understanding the difference and how to manage each type of bounce is a vital part of being able to keep deliverability up. Keeping your IP and sending domain in a good standing reputation is crucial to the success of your campaigns.

When an email is returned and flagged as a “Hard Bounce”, the email is permanently bounced back to the sender because the receiving email address is either invalid/expired or does not exist, and will not be able to be delivered.

When an email is returned and flagged as a “Soft Bounce”, the email is bounced back to the sender due to a temporary delivery issue. There are a couple reasons why the email may have soft bounced;

– Recipient’s mailbox is full

– The mail server is temporarily unavailable

– Rejected for content or sender reputation related reasons

– Your message was too large (images or attachments).

– Your message was considered spam.

One of the most important things in email deliverability is making sure you are cleaning and updating your lists after each deployment of hard and soft bounces.

Hard bounces should be cleansed immediately and not sent to again. From time to time, even if you have delivered to an email address in the past, it may eventually hard bounce as the email address is phased out or deleted.

Most email deployment platforms have auto-cleansing rules that will help remove hard bounces automatically so you do not have to worry about re-deploying to them.

Soft bounces are returned with a “Delivery Response Code” and/or a “Delivery Response Message” in the bounce log. This will give you a better idea on why the particular email “bounced” and you can update your database accordingly.

In general, it is encouraged to re-send to soft bounced emails.  Most email platforms are set-up to retry delivery on soft bounces up to a set amount of times until it is then considered a hard bounce and cleansed. Once you have tried to send to the soft bounced email three times, the best practice to suppress the record and not send to again.

If you are having a hard time cleaning up your database CAS can help! With our email verification and appending services we can make sure your campaigns go smoothly. Call us today 866-461-4693.