Hard vs. Soft Bounces, Error Codes & What to Do
When sending emails, it’s normal to occasionally run into delivery issues. At Raklet, we help you understand these problems by identifying the type of error and what actions you can take to resolve them (if needed).
In this guide, we’ll break down:
The difference between hard and soft bounces
What do common email error codes mean
How Raklet handles these errors
Practical tips for improving your email deliverability
What Are Bounces?
A bounce happens when an email can’t be delivered to the recipient's inbox. The receiving email server usually returns a reason, and based on that, Raklet classifies bounces into two categories:
Hard Bounces = Permanent Failures (Delivery Failed)
These mean the email cannot be delivered permanently, and no retry will be made.
Common reasons:
The email address doesn’t exist
The domain name is invalid
The recipient server has blocked delivery
Authentication (SPF/DKIM/DMARC) failed
Your domain or IP is blacklisted
Raklet Policy: If an email hard bounces, the address is automatically cleaned from your audience and excluded from future emails.
Note: In rare cases, valid email addresses may hard bounce due to issues on the recipient’s server.
Soft Bounces = Temporary Issues
These are usually caused by short-term problems and may resolve on their own. Raklet will retry sending several times before taking further action.
Common reasons:
The recipient’s mailbox is full
The server is temporarily down or overloaded
Greylisting (temporary deferral)
The message size is too large
Email blocked due to spam or content filters
Temporary domain resolution issues
Raklet Policy:
If there is no subscriber activity, we allow 7 soft bounces before converting it to a hard bounce.
If the contact has previous activity, we allow up to 15 soft bounces.
Transient (Temporary) Errors
These fall under the "soft bounce" category and usually resolve automatically. Raklet will retry delivery for up to 24 hours.
Error | Description | What You Can Do |
Transient-General | Temporary server failure | Wait and let retries run |
Transient-MailboxFull | Inbox is full | Try again later or contact recipient |
Greylisting / DNS delays | Delayed acceptance of unknown senders | Retry will happen automatically |
Permanent (Hard) Errors
These indicate the message cannot be delivered and won't be retried. Raklet marks the address as a hard bounce and removes it from future sends.
Error Code | Description | What You Can Do |
550 – Mailbox Unavailable / User Not Found | Invalid or deleted email address | Check for typos or contact recipient |
553 – Mailbox Name Not Allowed | Invalid email format | Fix the address format |
552 – Exceeded Storage Allocation | Attachment too large or mailbox full | Reduce email size |
554 – Transaction Failed | Generic permanent error | Check domain blacklists, spam score, or authentication issues |
Authentication-Related Failures
Raklet supports authentication standards like SPF, DKIM, and DMARC to prevent spoofing and improve deliverability.
Failures in these records may result in delivery errors.
Protocol | Purpose | What to Check |
SPF | Verifies sending server IPs | Ensure SPF includes your email service |
DKIM | Verifies message integrity | Make sure DKIM is properly signed |
DMARC | Aligns SPF/DKIM with the sender domain | Use mxtoolbox.com or your DNS provider to check records |
Troubleshooting Tips
✅ Test with a plain-text version of your message
🚫 Avoid spammy phrases like “Buy now”, “Free!”, excessive formatting or suspicious links
🔐 Always send from an authenticated domain (with SPF/DKIM/DMARC)
📤 Keep attachments small and relevant
📩 Use a valid reply-to address
❗ Check if your domain or IP is blacklisted
💬 Contact support if you’re repeatedly seeing the same errors
Email Bounce Reporting on Raklet
You can view bounce reasons and status for each campaign in your email report dashboard (Details).
The receipts for your bounces will be available in your email reports for 30 days after the email is sent.
Raklet cannot predict in advance whether a message will bounce — bounces depend on external server rules and recipient configurations.
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