In email marketing, a bounce occurs when an email fails to be delivered to the recipient's inbox. A high bounce rate not only wastes marketing resources but also severely damages your sending domain and IP reputation, and may even cause subsequent emails to be sent directly to the spam folder.
Understanding the difference between hard bounces and soft bounces is a must-learn skill for every email marketing professional.
What is a hard bounce?
A hard bounce means that the email cannot be delivered for a permanent reason . The mail server explicitly refuses to accept it, and this situation will not change over time.
Common reasons for hard returns
- Email address not found: The recipient's address is misspelled or has never been registered, for example, gmial.com is misspelled as gmail.com.
- Invalid domain name: The domain name following the @ symbol does not exist or has ceased service.
- The account has been permanently deleted: The recipient once existed but has since been deactivated.
- Email permanently rejected by the receiving server: The recipient server explicitly refuses to receive emails originating from your domain.
The dangers of a hard return
Hard bounces are the most severe type of bounce in email marketing:
- ISPs (Internet Service Providers) closely monitor hard return rates, and a warning is triggered if the rate exceeds 2%.
- A consistently high hard bounce rate can result in your domain being blacklisted.
- Service providers like Gmail and Outlook may directly mark all your emails as spam.
What is a soft bounce?
A soft bounce means that the email could not be delivered due to temporary reasons . The recipient's address itself is valid, but certain conditions currently prevent delivery.
Common reasons for soft rollback
- Inbox full: The recipient's mailbox has run out of storage space and cannot receive new emails.
- The receiving mail server is temporarily unavailable: The recipient's mail server is undergoing maintenance or is temporarily down.
- Email size too large: Attachments or email content exceed the recipient's server size limit.
- Temporary rate limit: You sent too many emails to the same domain in a short period of time.
- Content temporarily blocked: The email content triggered the recipient's anti-spam filter.
Features of soft rollback
Unlike hard bounces, soft bounces are usually recoverable. Most email delivery platforms will automatically retry soft bounces multiple times (typically 3-5 times within 24-72 hours). If the retry is successful, the email will be delivered normally.
Hard rollback vs. Soft rollback: A comparison
| Comparison items | Hard return | soft rollback |
|---|---|---|
| nature | Permanent failure | Temporary failure |
| Is it recoverable? | no | Yes, it may recover automatically. |
| Impact on reputation | serious | Lighter |
| Suggested handling method | Remove from list immediately | Keep it under observation, remove it after consecutive failures. |
| Industry safety line | < 2% | < 5% |
How to handle a hard bounce
- Remove immediately: Upon discovering a hard bounce, the address should be immediately removed from the mailing list, and no further emails should be sent to it.
- Create a blacklist: Add addresses that returned by hard bounces to the blacklist to prevent them from being re-imported in subsequent activities.
- Analysis of the cause: If hard rollbacks are concentrated on a specific domain, check if that domain has ceased service.
- Optimize the data collection process: Use double confirmation during user registration to reduce the number of invalid addresses entering the list.
How to handle soft bounces
- Wait for automatic retries: Most email platforms will automatically resend without manual intervention.
- Monitoring repeated soft rollbacks: If the same address experiences more than 3 consecutive soft rollbacks, it should be treated as a hard rollback.
- Check the email content: If there are numerous soft bounces, it may be that the email content has triggered a filter, and you need to adjust the subject and body.
- Control sending frequency: Avoid sending too many emails to the same domain in a short period of time, and allocate the sending rhythm reasonably.
How to reduce bounce rates at the source
The most effective method is to verify the validity of the recipient's address before sending the email .
Verification before sending
Use email verification tools such as AcctCheck to batch check recipient addresses before sending emails:
- Addresses with a status of "normal" can be sent with confidence.
- Addresses with a status of "unregistered" should be removed immediately to avoid a hard rollback.
- Addresses with an "abnormal" status should be handled with caution and may be tested individually.
Establish a regular cleaning mechanism
Email lists are not static. Users may delete their accounts, change their email addresses, or their mailboxes may be full. Recommendation:
- Perform batch validation of the entire email list every 3 months.
- Process the bounce address promptly after each campaign launch.
- Newly imported email lists must be verified before sending.
Use double confirmation (Double Opt-in)
A confirmation email is sent when a user subscribes, and the user is only officially added to the list after clicking the confirmation link. This ensures that:
- The email address is real and valid.
- The user does indeed want to receive your emails.
- Eliminate invalid addresses and typos at the source
Summarize
While both hard and soft bounces result in email delivery failures, they are fundamentally different. Hard bounces must be cleared immediately, while soft bounces can be observed and waited for. Rather than reacting passively after a bounce occurs, it's better to proactively verify the email list before sending, keeping the bounce rate below a safe threshold.
A healthy email list is the foundation of successful marketing. Regularly cleaning your list with email verification tools protects your sending credibility and ensures that every email reaches the right people.