What is the Difference Between Hard and Soft Bounces?
There are two primary types of email bounces - hard and soft.
A hard bounceⓘ refers to a failed email delivery caused by some permanent reason. A soft bounceⓘ, on the other hand, is temporary and will generally resolve with time or a manual fix.
What is the cause of a hard bounceⓘ?
The most common cause of a hard bounceⓘ is an invalid email address.
An invalid email address will always lead to a hard bounceⓘ as there is no destination for the email address. Here are some reasons for an invalid email address:
- The email domain does not exist
- The username doesn’t exist on the email domain
- The address uses incorrect syntax
- The address contains a typo
What are some causes of soft bounces?
Soft bounces can occur for several reasons - all of which are temporary and can be resolved. Some examples include:
- Spam prevention technology such as greylisting
- The mailbox is full
- The receiving server is temporarily down
- The spam filter rejected the email because of spammy content in the email
- The email file size is too large
You can overcome many soft bounces by simply reattempting the email send. For example, greylisting only initially blocks emails from unknown domains but will allow the email after a set time expires (usually 15 minutes). You can reach the inbox successfully with no additional action by configuring your SMTP settings correctly to retry sending automatically.
You’ll need to revisit your email for other issues like spammy content. Once you identify what’s activating the spam filter, you can adjust your email to reach the inbox.
What’s worse - hard or soft bounces?
Hard bounces will cause more damage to your email sender reputation. However, soft bounces can still make an impact.
Soft bounces, however, allow some room for grace. When you encounter greylisting, for example, you can automatically retry sending the email and reach the inbox within a specific period.
However, it’s important to note that soft and hard bounces are rolled into one metric. So, the more you soft bounceⓘ emails for reasons like content or file size, the more they can negatively impact you.
Learn more about hard and soft bounces - and how to deal with them.
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